C. S. JONES SIGNALLING SYSTEM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81-00120R000100010003-3
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 12
• Document Creation Date: December 22, 2016
• Document Release Date: December 8, 2003
• Sequence Number: 3
• Content Type: CONT

Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
a' 241 FIG.2c
J, fa f5 J?4 15 Y,
FIG.2 b
rxx-~, r~XX~~
FIG. 2c 0
f5
,r ?
DISTANCE
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
CLARENCE S.JONES
INVENTOR
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
United S Cates Patent Office 3)054,100
Patented Sept.11, 1962
Clarence S. Jones, Los Altos, Calif., assignor to General
. Precision. Inc., a corporation of Delaware
Filed June 4, 1958. Scr.No. 739,909
26 Claims. (Cl. 343-6.5)
coil moves sufficiently close to any. one of a plurality
of passive response blocks distributed along the. right-of-
way; certain of the radio frequency bursts operate reso-
nant circuits within the response block to furnish power
to operate a small responder oscillator, which transmits
a return signal on a further radio frequency. By selec-
blocks, the responder oscillator will provide a serial pulse
code signal for reception by a receiver associated with
the interrogator useful for identifying each response block..
As well as using the interrogator. on a vehicle to deter-
and more particularly to apparatus for identifying the
location of a first object with respect to one or more of
a plurality of second objects. The invention may be
utilized for a variety of different purposes, a number of
which will be mentic'ed below.
In the transportation and materials handling fields in
general, and particularly in the esTie cnt running of a rail-
road, it often becomes desirable to know such informa-
tion as where each train is at any time, or with what
velocity the train is moving, or where individual railroad
cars are located. Sometimes it is of great advantage to
determine the location of goods or materials carried on
railroads, trucks or conveyers.
A considerable saving may often be effected if a central
agency is apprised, at all times, of selected portions of
the above information, since the operation of railroad
or trucking business involves Iong distances covering a
large territory without readily available communication.
equipment. For example, scheduling of trains may be
considerably simplified by remotely observing the density
of traffic at crowded switching points. Information as to
the location and identity of available railroad vehicles
stored on sidings is immensely useful in determining the
type and amount of freight space available at any of the
loading centers. Information as to the location of par-
ticular goods, such as raw materials or cattle shipped
across country or, several trains or trucks, helps the
recipient to make necessary arrangements for unloading,
storing or the like.
Referring now more specifically to the railroad busi-
ness, it has heretofore been suggested that radio links be
established between each engine or each train and a cen-
tral a;ency in order that the operators, or the attendant
personnel thereof, be able to inform the central agency
of their location. While such systems have been quite
useful, their effectiveness has been limited by the fact
that each train operator must be relied upon always to
furnish accurate information with regard to the loca-
tion of his train.. Additionally, the location of selected
special purpose equipment, such as refrigerator cars or
heavy-duty freight cars. may require further radio links
situated proximate to such coupling points to be operated
by railroad yard personnel, since the train operator usu-
ally does not have the means or responsibility to ascer-
tain or keep track of the identity of the individual cars
on leis train.
The need for an automatic signalling system for fur-
nishing accurate information wits regard to train or truck
location or goods identification to a central agency has
long been, recognized, and carious systems have been
proposed. As far as I know, none have been very :sue-
ccssfal, except the system disclosed in my copending ap-
plication Serial Number 715,899, filed February 18, 1958,
for '-Signalling System," which application is assigned to
the same assignee as the present invention.
The specific system disclosed in detail in my eopending
application may he E7 ,,id to c, mprise an interrogator-re-
spo_,der system. utilizing an interrogator apparatus to ap-
ply radio frequency energy to a transmit coil carried on a
movable ctcviet such-as a railroad vehicle. In my pre-
vious application, successive bursts of radio frequency en-
ergy are tranyr?itted_on different. frequencies, which are
cyclicly repeated. As the vehicle carrying the transmit
mine vehicle position with respect to a plurality. of fixed'
locations, my previous system contemplates locating the.
interrogator at a fixed location to identify objects pass-,
in, by which are provided with suitable passive response
blocks and which pass within the signal field of the. in-
terrogator.
Rly previously disclosed basic system offers an ex-
treme advantage over prior systems in that it uses pureIv
.--
accurate-or unreliable, so that numerous remote stations or locations may be provided with response means,witli
out attendant provision of electric batteries or wired
power sources. While passive response units have here-
tofore been provided elsewhere, all of these of which; I
am aware required precise physical alignment and were
adversely affected by various environmental factors.
While the invention of application Serial Number
715,899 admirably accomplishes its purposes, and while
30 it is ideally suited for a wide variety of applications, cer-
tain applications benefit from modification of rriy earlier
system. For example, the specific interrogator disclosed
in detail in my earlier system transmits a series of radio
frequency signal bursts, each of a different frequency,
33 with a burst of radio frequency energy of a further fre-
quency interposed between each code signal for automatic
gain control purposes. If a large number of differently
coded response blocks are to be used, so that the system
may employ a digital code having a relatively large num-
40 bcr of binary digits, a large number of different interroga-
tor frequencies must be transmitted successively. This
requirement may be troublesome when the system is
applied to the identification of very rapidly moving ob-
jects, or the identification of the location of an object
115 which moves rapidly with respect to a plurality of fixed
locations. -
In order to allow the use of economical circuitry and
still preserve system reliability, the title length of each
radio frequency signal burst must be maintained at or
50 above a minimum value. In the case of rapidly moving
bodies, the interrogator transmit coil and response pickup
coil may remain sufficiently close to a response block to
interrogate the block only during a short period of time,
so that an insufficient number of interrogator frequencies
55 can be transmitted if each frequency is allotted its re-
quired duration. The present invention is in some re-
spects an improvement over the previous invention since
it overcomes the described Limitation by interrogating a
plurality of digits simultaneously.
00 In certain ether applications signalling systems of this
nature may be used to transmit data relating to the posi-
tion of a movable object with respect to successive fixed
locations. Sometimes it is desirable to be able to deter-.
65 mine the rate at which the object is moving by noting the
rate at which it passes by a number of fixed stations. If
a precise velocity determination is to be made at a given
instant rather than a mere average velocity determitLa-
tion. it may be understood that vehicle location must be
70 noted at different locations which are very close to each
other. If response stations are located very close to each
other, and if vehicle speeds become great. ehough,. it is
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
digits of a responder simultaneously with radio fie quency improved s;cnalling system which is reliable in operation,
energy having a single frequency by providing each re- 5 simple in design and economical in construction.
sporder with a selected plurality of response oscillators,. Other objects of the invention will in part be obviotrs
each one of which corresponds to one digit. In this and will in part appear hereinafter.
manner, the interrogation time is a minimum, since only In a;cordance with one embodiment of the invention,
a single burst of radio. frequency cnergy provides a an interrogator unit, also called the interro atop, is
digitally coded response signal identifying a responder Io mounted upon a moving vehicle whose location is to b
uniquely-: In such a system, the interrogator receiver determined at fixed intervals. The interrogator has a
means instead. of the interrogator transmit means utilizes trjnsmitchannel which oririnntes an radiates a radio
a broadly tuned coil which is responsive to the radiation frequency carrier signal hating a plurality of audio fre-
from each ore .of the selected plurality of response oscil- quency,modulating signals ,.modulated thereon. A num-
l'ators. When this proposed system is compared to the 1 her of response blocks, also refs red' to as responders,
system of my above ,mentioned copending application, may be located at various intervals along a railroad track
it is seen that the burden of generating the plurality of or roadbed over which the vehicle passes. In the case
.code frequencies has. been shifted from the interrogator of railroad tracks, the preferred position of each re-
unit to the response block, with simplification of the spopder is the top or inside of a selected track tie.
former, but with morecomplex structure in the latter. 20 . The location of and the distance between individual re-.. -
)n many,. applications: of signalling apparatus. of this spouse blocks is largely a matter of choice determined by
nature, large numbersm of response blocks are needed and what particular points identification of location of the
only, a few interrogator units. are needed- In such in- vehicle is made. As will be explained below the num
stances it : becomes uneconomical to increase the com- ber of response blocks whic't may .b: utilized throughout
plexity of the response blocks. 25 an entire railroad network arc limited, at least to some
My aboveraentioned eopending application discloses; in extent, by the number of digits of the digital code used.
'detail an. interrogator -responder system using signals of As will become clearer from the detailed description of
twelve. different radio frequencies in order to provide this inventioneach of the audio frequency modulating
identification by means of a digital code. having ten digits- signals provides one digit of a digitally coded identifica-
It the twelve frequencies are spaced so as not to interfere . 30. tion number.
With each other and not to interfere with other radio sig- As stated above, the respective position of the inter-
nailing devices, it will be seen that they require a given. rogator and responders may be exchanged so that the
amount of the R.F. spectrum. The. present invention
. allows a great reduction in the required bandwidth- By
using a single interrogator R.F.'frequency and a single
response R.F. frequency in the present "invention, I am
able to transmit a large amount of data using much less
-bandwidth. In my previous system my interrogator unit
radiating means had to be broadly tuned, with attendant
loss in selectivity, because it had to transmit nurnerQus
different radio frequencies. In a modiled version of my
earlier invention, a plurality of R.F. response frequencies
were required, so that my interrogator receiver input cir-
cuit had to be broadly tuned. The present invention al-
lows both the radiating means and the receiver means
to be sharply tuned, so that stronger signals may be trans-
misted and received without increasing the cost of my
transmitter units, thereby increasing the signal-;o-noise
ratio and accuracy of my signalling system.
It is therefore one object of my invention to provide an
improved signalling. system for automatically identifying,
locating and numbering a plurality of objects.
It is another object of my invention to provide an im-
proved signall r..g system of the type in which a plurality
of digits are interrogated simultaneously.
It is still another object of my invention to provide an
improved signalling system for interrogating a plurality
of digits simultaneously utilizing a simplified response
block.
It is a further object of my invention to provide an im-
proved signalling system wherein a simplified interroga-
tor unit interrcga+.?cs a response block with a burst of
modulated radio frequency.energy of a single frequency
and wherein the response block responds thereto with a
burst of radio frequency energy of a sir?ple frequency. in
which the sig sal provided by the response block is capable
of uniquely identifying one of a large number of response
it is a further object of,my invention to provide an im-
proved signaling system for interrogating a plurality of
digits simoltar.:ously wherein both the transmit`coib and
the pack-up coils may be sharply tuned so as to allow
greater sensitiv by and accuracy.
interrogator unit is fixed and each: of the moving ve--
hidles carries a response block.* Such an arrangement is
35 preferred when goods are moved by conveyor or the like
over or past the interrogator, or when freight cars are to
be classified upon entering or leaving a switcbyard.
When the interrogator is located near or directly above
a response block, the pick-up coil of the responder , re-
40 ceives the audio modulated interrogator, carrier. and
demodulates the same to provide a response-actuating
signal therefrom. This response-actuating signal may
comprise a direct current power. component attributable
to the rectification of the radio frequency carrier and a
composite audio frequency signal component attributable
4a to the individual audio frequency mterrocator signals
which modulated the carrier. The response-actuating
signal is applied to a responder coding means which
passes or suppresses selected ones of the modulating sig-
5,J nals. The outr_ t signal of the coding means provides a
digitally coded response-actuating signal by virtue c-' the
selected modulating signals remaining on the output sig-
nal. Each different responder is coded so that it passes or
suppresses different ones of the modulating signals, so
that the digital coding of each output response-actuating
5o signal identifies a particular responder.
The digitally coded response-actuating signal is then
utilized to power a response oscillator which provides a
further radio frequency carrier having modulated there-
on those of the audio frequency modulating signals passed
f0 by the coding means. The coded response-actuating sig-
nal is the solo power required to operate the response
oscillator, so that no batteries or wired power sources
are .necessary.
The coded carrier radiated by the response oscillator
65 couples electromagnetically to and is detected, by a re-
ceive channel, which may be part of or physically located
with the interrogator. in some applications, it may be
considered advantageous to rectify the carrier to provide
50 a voltage for automatic gain control of the transmit char-.
net. The signal received and detected by the receive
channel is applied to an, audio frequency discriminator
device which has a separate output channel for each audio
It is still a further object of my invention to provide frequency modulating signal provided in the irterroga cr
'an improved signalling system utilizing a simplifed re- 75 transmit channel, each discriminator outputchangel be-
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
ir?g sclcctively responsive to a respective orindividu l 1aia mavt
o it usual itte3, ifple edsdlifromste intone=
o frequ
f the
-___ _
audi
one o
decoded audio signal, which 1s a mixture of selected audio Bator to a remotely tom ,red c nacre
The term carrier or ca Tier signal as used in this appli-
frequencv interrogator signals. is thereby rnscrar :bled
rated into individual audio frequency interrogator 5 cation is intended to mean any wave suitable for being
The term
als
l
ti
d
.
ng sign
a
or sepa
u
si nrals, and after suitable rectification. an out,-.'! vol age modulated to transmit mo
appears on each channel associated with a selected audio modulating signal as used in this speci,`cction is any wave frequency interrogator signal. The prese suitable to modulate a carrier. It is also common prac-
of or ab_sen~e
of an output voltage on a chi r.nel may he indicated upon tice in file art to refer loosely to the modulated and the
a code register as either a "one" or a "zero" for pro- 10 modulating waves as radio-frequency and audio-frequen-
viding a digitally coded nuMber which deter:nir.a unique- cy sigmis to distinguish between their relative frequencies.
ly the p:=rticular response block being interrogated. Such ierminclogy has been adopted it the remainder of
The digital code set into the code register may be trans- this specification, it being understood, however, that
milted to a centtal agency by any of the many well- audio-frequency' is used herein in its widest sense and does
known data link systems. Since the central agency in 15 not confine the'range of the modulating signals to the
a railroad signalling system of the kind here. described audible ran e. of the interrogator NO which provides
usually desires information from a lane number of rai!-
reed trains., and since it might be llnecon^I:1;Ca1 to pro- the uncoded interrogation carrier is also referred to as
vide separate data link receivers for each interrogator, it the interrogator transmit channel, and may include a plu-
often will be convenient to add an identification register 20 rality of audio frequency or modulating signal oscil-
to. The code register. An identification register may be lators, only three eof which chuare s rs 1i0,~ 1n 1, andtive respectively
provided with each interrogator, so that signals whit.. designated by
identify the interrogator are sent to the central agency to Each audio frequency signal oscillator develops a signal
specify which interrogator is "reporting" to the central of a different fr-.agency as shown by the designations e agency. This additio.a increases the number of digits `5 lfl, f2 ion ban dvf the actu i lob compevidentifromqu ncdy crip-
which must be transmitted by the data link system by
the nur.:ber of digits necessary to identify a pzrucular lators utilized depends on the number of responders to
interrogator unit. The additional register, howeNcr, does be interrogated. Each of audio frequency signal oscil-111 not eoriplicate the interrogator, since it is not a part of tutors -0 130, be an 112
to as am vi diode so lin'erput
the interrogator, and only conies into operation in. con- 30 gator signal or just interrogator signal. An audio-inter-
nec-icn with a data link sysicm.
Fora fuller understandiu.g of the nature and objects of rogator signal attenuator may be associated with each
the invention reference should be had' to the followir? audio frequency oscillator. The plurality of attenuators
detailed description taken in connection with the accom- 33 are designated respectively by reference characters 114,
ponying drawings, in which: 115 and 116. The individual interrogator signals ap-
FIG: 1 is aschematic electrical block diagram illus- gearing at the outputs of attenuators 114, 115 and 116
Crating one embodiment of the signalling system of this may be intermixed is a conventional audio signal mixer signa l
invention as it might be used in connection with a rail- 117ch ispo provide
d[ tad cupon a ompoSite audi intern carder such
road data transmission system;
FIGS. 2a, Zc, 2e and 2g each are electrical schematic 40 as may be generated by radio frequency oscillator 113
diagrams of several embodiments of coded passive re- by modulation means such as a conventional modulator
sponders which may be utilized with the signalling system 11The output signal from modulator 119 comprises an
of this .2b, 2d, , 21. 21r are binary code diagrams of the audio-modulated carrier, which may be applied to a
FIGS. 2b,
several responder embodiments of FIGS. 2a, 2c, 2e and 45 variable gain device such as attenuator 120, controlled
2g and are included to aid in the explanation of the by G.C. signal) automatic gain cntronsig al (al o refe red to purpose an
coding techniques utilized in the responders, and
FIG. 3 is a graphical illustration useful in understand- providing automatic gain control and the method of.
ing the operation of the automatic gain control feature developing the A.G.C. signal will be explained below in.,
of this invention. 50 connection with FIG. 3.
The novel features whib are believed to he character- The output signal from attenuator 120 may be suit-
istic of the invention; h th as to its organization and ably amplified. if desired, by an amplifying means such
method of operation, together with further objects and as power amplifier .122 and utilized to excite interrogator
advantages iherecf, will be better understood from the transmit coil 123 with the carrier modulated by the com-
following description considered in connection with the 55 polite audio interrogator signal. Each of the individual
accompanying drawir:_s in which several embodiments of cornper:ents of the transmit channel are in themselves
the invention are illustrated by way of example. It is known to those skilled in the art and therefore need
to be expressly understood, however, that the draw- not be further elaborated on.
ings are for. the purpose of illt'stratien and description Attenuators 114, 115 and 116 provide individual in-
only and are not intended as a defirition of the limits of 00 teriogator signal amplitude control to compensate for
my invention. ? frequency sensitive' components in the signalling system.
Referring now to the drawings, and particularly to so that all interrogator signals ultimately received may
FIG. I thereof, there is shown an embodirunt of a have approximately the same signal strewth. The com-
complete signalling system in accordance with this in- Vitiation of audio frequency signal oscil.'ators 110, Iii
vention comprising an interrogator IOa for providing a Oa and 112, attenuators 114, '_I5 and 116, mixer 117, mod-
_ ;end for decoding a re- ulator 119, radio frequency osciilatu: 118, gain device
ceived modulated response carrier, a respo I,G L -_ -..?r ???-? -
for providing the modulated response carrier upon re- fore provides an interrogator transmit nrean""for -en-
eeipt of tie modulated interrogation carricr. and a data 70 crating and radiating a radio frequency carrier having a
link system 104 which may be utilized to transmit info:- plurality of interrogator signals modulated thereon.
mation obtained from decoding, the modulated response Responder pick-up coil 125 may be a tuned circuit
carrier to some centr:_l information-gal~ierirg center. resonant at the radio frequency of the carrier applied
As will he obvious from the dot fled description to interrogator transmit coil 123, and therefore coil 1_5,
below, the dat- !ink c.c!em 104 is oalioral and.is here 75 wt.en tuned to the frequency of the interrogator carrier,
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
 fief- in this manner respKMder pick-up coil 125 ccm- vhigh is :'.:a olc~r.t::e _e' t' itie a caztrcl s',"-Ilal or,
friscs a responder pick-up meats or a tuned circuii uIcrnatic pain control a coin ,._si_, audio
i 1eans responsive tc the carrier from th, interr.i^_a'or i:nrrro_ator gill of
transmit means which is ci,._rative to develop a response : , :? udio fr,_:;cca } 1 er c s s .
signal. The response signal from the pick -tip coil n.-y The c-mt'^sit, ut:er.c_a:or gu al `r_m Ch- ,ce,Ondzr
1b3 applied to a demodulator 136 which rectifies the re- or
6E ~'c'CI radio frequency C rile!' to derive a respon"C-act J- int?_rro_ator ,sign is 1"y a p*Ur'-l't . c -=rrC:'r bind-p"'Ss
atin signal having the composite interrogator signals audio frequency fii,cr': The plura'ity -
ni-cdulated upon the rectified carrier votta, 0 of iiltcrs as such is rcf.:r;ci to thtie'a a~ a di crniirr.tor
The responst-actuating sip t;!l may be irtprers d up:n n errts or as a er. Ts ^: ccur, C
S ceding means such as eeiiin network 117, which i s c~,-:t.tl-at for each , I:Jiu frcgoenr ^_.. - nr sigh as
operative in removing or suppressing certain ores of the 110, there must be ? cc:rr,:_ nd ne fi:ter. such as 1~4.
plurality of interrogator signals making up the cot-n- so that p filters are rcga:e,J alto _t :er- The f dcsi_na.-
8
I 1_
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
cal for A.G.C. purposes will he discussed in'c'?etaii be;o;v a single composite i 1fi, apart
in connection with the automatic gain control,-Jicuit. In The cu.-nut v. hopes frc?rn the auJia f::tern dete-
this manner pick-tip coil 130 and receiver 1 2 p ins i.'.e an tors 134, 135 and ' ;5 b.i-g in.rt?_;till c; tee, t;,e} fit} b
:
interrogator.. receive moans which is oper;itive to receive 75 I:pplied directly'to~the digit stage, 137, 133 ar,d 1?.9 of
Tosite lrtterronator signal. As will be c-sp!nined in c.. j plot! S ua wn for each alltar l;:d gates the center frcque cy _
siderable detail in connection with FIGS. -_'a to of its p. ss band.
ceding network 137 may comprise a girt}' ina:iou a`' E.:cth filter of the discri:rmater m ay be of a Conven-
audio frequency tuned circuits resonant at scie ?c i tion,,l design sect n,-.y ca: opr .F: either a p ral'?el-tuned
te-irrigator signal frequencies, which permit only sr clod or serfs-tort J nc',Ic i)r-f p:icitJr net',;ork. In certain
6rfes cf the int?_rrogatiou signals to pass therethroiigtt. 20 instances it m:sy be desirable to utilize an active filter of
Ili ether words, coding nc,work 121 comprises a cod- the viol! know l type cc?i?np;?ised of a feed-back rimpiifi.rr
in- means responsive to the response-actuating signal liavii:^ a frequency deper('?fnt n_tw ri: iil its feed hack
which is operative to suppress predet^rrnined Ones Of (hr path. Suitable frequency dc;) nderi rwt'serks may be
audio interrogation signals and thereby piovi ivs it coded- found in chapter 10 Of ' VccUUm Tube Am :!ifiers," vol.
resjso se-actuating signal including only those of the 25 13 of the Radiation Laboratory Series, published by Ale-
interrogator signals which arc characteristi.- of tl;e re- Graw-hill Book C:-ri,,%.ay, Inc., 1943. Each of the
sporder. tuned circuits is resonant z t h dill,:rent one of the inter-
The coded response-actuating signal may :hen be' ntll- 1?olplor signals. arid off: ;ti :'e to pass only the Inter-
i:ed to power a response oscillator means, nigh as oscil? ,ogalor signal at. the rc~onnr.t frequency of the tuned
lb,tor 123, having a tuned circuit resonant at a irequency 30 circuit, Each filler may include a rectifying stage hav-
different front that of radio frequency oscillator 11S, ing a diode to derive adirect curre:a voltage as th_t
for providing a radio frequency response carrier having co,icd output voltage..
the selected interrogation signals modulated thereon. The Or course, if codi:?g network 127 has supprccscd a par-
response. carrier is impressed upon a responder transmil ticul..r audio interrogator signal, this n-rticular signal is
coil 129 which may comprts.e a suitable tuned circuit c:'.::- 33 not presented as par, of the composite audio sig:pal rc-
ment for inducing the modulated response carrier i :ta ceived by pick :p coil 133. and consequently, the filter
pick-up coil 130 when in close proximity to transmit coil associated with that particular snupressed audio ere-
SZ9. A more detailed description of rest Gilder IJ'_ gtlcncy does not provide an output va:t'=ge? Thus it will
is offered in connection with FIG. 2 wherein responder be seen that the presence or ab:.rnre of given audio fre-
tranmhit coil 129 comprises the tank circuit,of the response ?~ R u_n-nett in tine signal received frcri ., , given respoacr 214 000, the oscillator 2230 is still! required to provide a radio
'
v)hich smoothes out the interrogation carrier. For c%"- C3 frequency respCnsC carrier. The rectified interrogator
ample, if the interrogator c:irri'-:r feegimercy is "') kilo- carnie co aponent mist always b ssmc;?ent!y large to set
,Cycles per second, interro ator s n .is nl`ove arpro'a- oici!l:r.or 2.30 in:o C ci 1a10 s. Also, the degree of
?~1T'.tely 30 kilocycles 5ho,ilc be wasted to p rev'ent reeds- I adulation or the inodul i o^ factor must not be So large
c no thhereof. A typical selcction c.f 10 inicrro :aar as to ;:;ierfere ..it}i.tha go'sz" "e of oscih", r 230:
inductor 23. and caapaci?
: r , match is h-i-monic related to t'1P The t;:nzd c:rcu;t comp -:-2
.Zuencies, none o, t',, ai.
f:..
ctl-ors, In kilocycles per secoi-J is as. ello'v.s: 2.1, 25, - ~~ to,- 232 may be utilized -ponder transmit coil 129,
3.1, 3.7, 4.3, 5.5, 6.6, 7.7, 8.1'J.6. FtG, I. so, that no ausiiiary :ransa:it :oil is required. Of
the efore course, ar! anten may be coupled to this tuned circuit
Ceding n twork 220, 'as d !bed ove, is
s=ea. (o be 'a codin. me:-is ons ve to th_ rC.punSC- to provide the actual radiating, elerrtrent if so desire 1e
;t_ri,iting 5i Approved For Release 2009/04/10 :CIA-RDP81-00120R000100010003-3
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
(namely the melt u!ated respon,e carrier) is applied to ulustra'es the bin,., y code cf coding network illustrated
tuned relatively sharply to provide-high gain and a re- There has been de-cribcd a signalling sy'stenh wherein
s,iltirtg saving ir. Power. For the sanie reason transmit h e ; ogetor in re )[1ve motion with a plurality of re-
coil 1-,3 and pick-tip cells ?125 and 130,'FIG. 1, may be - !ponders identi.ies e-!eh respond r by a digital code. The
rc'ativelJ sharply i=shred. - id_:ui;tcation is acconplis',led by interrogating each re.
The co-rbil:.,ton of oscillator 2.',7 inc.r!dir.a the ht-cd spode block at the li r_ of closest approach with a plu ?
circuit comprising inductor 231 and ct aci'or _32. p-o- edify of audio f"equcnev signals modulated upon an in-
vides th:refor, a responder oscillator means re_ponsi?.e tcrrogation carrier baking a single frequency. Upon
to the coded response actuation si n81s which is opera- 1n recei ing the interrog:.;'On carrier, any given responder
hive to __nerate and radiate a r:d o fro _e e respansa pro%id_'es-a rest once carrier havirg*a unique combination
carrier having selectively passed interrogator n-: !s of, the au(iio freaacncy interrogation signals modulated
medal ae3 they on, the particular cotbination of inter- thereon. The interrogator picks up the response carrier,
ro eter signal; modulated on the respome carrier being and by sens ng which audio frequencies are present on
uniquely related to the )articular responder containing 15 and which arc -absent from the response carrier, a digital
the oscillator means. reps es ntation identifying the responder from which the
FIG. 22h illustrates the digital code which the responder r=epo-^se.carrier is being received is produced.
of FIG. 2a wo;dd set on code register 1!9, FIG. 1 . The While the specific e-ht:codiment disclosed above illus-
tuned circuits f.j. f;,: f?;, f3 and f9 permit trans-?his_ion of trates a system in which the carrier information frequen-
th intecrogtttor signals Navin; frequ_iades fi. f fa, fs 20 Gies are amplitude-modulated by the audio code or digit
throi:gh coding nettvork 220, Therefore, selnetcd inter- frequencies, it will be apparent to those skilled in the art
rogation signals ft,, L. fa. fe . provide the "o; es" at as a result of this disclosure that phase or frequency
the output leads of associated dii,ercitce amplifiers, such modulation May be substituted is parts of the system with-
as those shown in F.M. I and design' mated by reference out dcpa_?ink fro-*n the invention.
numerals 14?, 143 and 144. As previously mentioned, 3 A number of known circuits are available in the prior
each re-,ponder is provided with a'diffc.rc-t coding net- art to provide the clenhents. shown in block form in thy.
work having a ctifictent number or kird or both of audio c?r::^dings, and my abovementioned copending application
tuned resonance circuits to provide a coded response- discloses a number of exemplary circuits which may be
actuating signal having a unique combination of audio used.
frequencies. 30 bat I claim as my invention and desire to secure by
FIGS. 2c, 2e and 2g show different embodiments of Letters Patent is: -
coding networks constructed in accordance with this in- 1. A passive responder unit capable of relative move-
s?ention ; hick may be substituted for coding network meet with respect to an interrogator apparatus and oper.
220. FIG. 2a. The terminal designation A; B,~C, and D able to provide a response signal having a coded charac-
of FIG. _n is retained to- designate the connecting ter- 35 teristtc, said unit comprising in combination: first means
minals of the various coding means. The coding means for receiving a first carrier signal emitted from said inter-
shown in FIG. 2c utilizes two aeries tuned ire?active- ro afar apparatus, said first carrier signal having a plu-
capacitance circuits fh and fa resonant respectively at the rality cf fi::ed discrete signals of different frequencies
audio frequencies ft and fi. if a response-actuating modulated Cie-non; second means coupled to said first
signal is impressed upon terminals A and B, the result- 40 means; and response-signal generating third means con-
ing coded response-actuating signal will not include netted to said second means and operable to provide a
audio frequency interrogator signals ft and f., since at response carrier signal, said second means being opera-
those frequencies tht tuned circuits ft and f.t are resonant the to selectively eliminate or pass selected ones of said
and effectively establish a short circuit across the con- discrete signals to said :hied means and operative to de-
ductors a'--? and 241. 171G. 2d graphically ilius'.rates the 45 modulate said first carrier signal to provide the operating
digital code of the coding network of FIG. 2c from power for said third means.
which interrogator signals ft and f , are eliminated cr sus- 2. A responder unit in accordance with the structure
pendcd. of claim I wherein said first means includes a parallel,
The coding network illustrated in FIG. 2e utilizes a tunad inductance-capacitance circuit resonant at the fre-
combination comprising two parallel-tuned inductance- 5o quency of said first carriem
capacitance circuits ft and f3 serially inserted between 3. A responder according to claim 2 in which said
terminals A and C, and two series-tuned inductance- second means includes a demodulator connected to said
capacitance circuits f{ and f; shunted across terminals A toned circuit for dernoctulating said first carrier signal to
and IS.' The par:?f'el-tuned circuits, resonant at the fro- provide a response-actuating signal comprising the recti-
quencie_ ft and f3. will suppress the passage of irterro- 35 component of said first carrier signal modulated with
gatie^ signals having frequencies 1 and f3. The series- - said plurality of discrete signals.
tuned circuits, resonant at the frequencies f.: and J. will 4. A responder unit according to claim 1 wherein said
suppress interrogation signals having frequency f4 and second means comprises a number of tuned circuits each
fs. FIG. 2f illustrates the digital code of the coding net- of which is resonant at a different one of the frequencies
v,ork.".listreted in FIG: 2e. The only intcrrogatcr si^- CO of the said selected modulating signals.
nals appearing across terminals C and' D are interrogator 5. A responder unit according to claim 1 wherein said
signal having frequency f2 and of course those having a second means comprises a number of tuned circuits each
frequency higher than fs. of which is resonant at a different one of the frequencies
FIG. illustrates a coding network utilizing two of the non-selected modulating signals.
parallel-tt.ned inductance-capacitance circuits fi and f3 63 6. A responder unit according to claim 4 wherein said
respectiv.?1,- tuned to the frequencies ft and f3 of the in- tuned circuits are connected in series with one another
terrogati:rt signals to he transmitted and connected in and wherein each of said tuned circuits comprises a par-
series across tear:pals A and B. Instead of u!-:zing- a aliel=utned inductance.-capacitance network.
tuned circuit for elininatin_ a paciicuiar interro ation 70 7. A responder et;it according to claim 5 wherein said
signal: tide tured circuits in this embodiment pass selected tuned circuits are connected in parallel with one an-
interrogation signals. All. interroen for S;1-11'$ _appearir.e other and wherein each of said tuned circuits comprises
between A and B except those having frequencies ft and series-toned inductance-capacitance net..'ork.
f3 w!ili ire effectively short circuited across the conductors 8. A responder unit according to claim 5 wherein each -
respective1 connecting terminals AC and BD. FIG. 4!s 7 of.said toned circuits are connected in series with one
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
3,054,100
n
a
' i slgra , an os,
-
lt
ator. 75 gad said respanster p:cs-up means being a maximum
p
c
s .
ere"
hots:.
an
providing nets coupling be:v.een s,.;d intcrrogator transmit means
om . 1
thereby a coded res on e--tu
t;
'l
,
- -
- - -- ----- --._ ....?,?..n...1 u.L,uUalp' iJIL -up
direct voltage comp:nent -.^.d selected ones of said alter- me.ins excitable by rat said first carrier, the electromag
irr voila corm ?
on
~m
th
i
h
d
.! Q --- --.-: ------ ..u,. zZ n ;,u,unly OI.au010
plurality of said interrogator signall; coding means frcquenc?r interroe for cn n,,1, ,,,,ten..,.,,, ..1.,.____- _
a 4j
another and wherein each of said tuned circuits comprises means coupled to said coding nteans and responsive-to
a parallel-tuned inductance-capacitance network. said coded response-actuating signal for generating a sec-
9. A responder unit acco ling to claim 5 wherein some and-radio frequency carrier having a frequency different
of said tuned circuits are connected in series with one from that of said first carrier and being modulated by
another and wherein the remaining of said tuned circuits 5 those of the interrogator signals whose frequencies are
are connected in parallel with one another and wherein cornmensu rate with said selected ones of said alternating
said series-connected tuned circuits comprise parallel- - voltage components.
tuned inductance-cape chance netwo-ks and wherein said 15. A passive re t- :nder unit adapted to be excited
parallel-connected tuned circuits comprise a series-tuned by a first-radio frequency- carrier having a plurality of
inductance-capacitance network. lp audio frequency inte_ro-ator signals modulated thereon
10. A coded responder unit comprising: a first tuned and for generating a second radio frequency carrier hav-
circuit means for receiving It first radio frequency ing only selected ones of said plurality of audio fre-
carrier corresponding to its resonance frequency hav- quency interrogator signals modulated thereon, said re-
ine a plurality of fixed discrete audio frequency signals sponder unit comprising; a parallel-resonant inductance-
modulated thereon. said first tuned circuit means includ- 15 capacitance tuned circuit having a resonance frequency
ing carrier demodulation means to provide a response- corresvending to said first carrier; a rectifier connected
actuating signal including audio-frequency comnponents in in series with said tuned circuit; a radio frequency smooth-
accordance with said audio-frequency signals; coding ing capacitor connected in parallel across the series com-
means coupled to said first tuned circuit means for sun- binatirn of said tuned circuit and said rectifier, the. com-
pressing selected ones of said audio-frequency signals 20 bination of said tuned circuit, said rectifier and said ca.
front said response-actuating signal; and a second tuned pacitor being opera::ve to provide a response-actuating
circuit means coupled to said coding means and respon- signal having a rectified carrier component and audio
sive to the response-actuating signal as modified by said components corresponding to said audio frequency in-
coding means for generating a second radio frequency terrogator signals; a coding means including a plurality
carrier having a frcoutrcy different from that of said 25 of audio frequency tuned circuits responsive to said re-
first carrier and being modulated by the non-suppressed sponse- actua:ing signal. said coding means being operative
audio frequency signals. to suppress particular ones of said audio frequency inter-
11. A coded responder unit comprising: a tuned cir- rotator signals and operative to pass others of said audio
tuft means including a parallel-resonant inductance- frequency interrogator signals, thereby to provide a
capacitance pick-up coil for receiving a first radio fie- 30 coded response-actuating signal having audio frequency
quency.carrier corresponding to the resonance-frequency components in accordance with said others of said audio
of said pick-up coil, said first carrier having a plurality of frequency interrogator signals; and oscillator means re-
audio frequency interrogator signals' modulated thereon, sponsive to said coded response-actuating signal and op-
said tuned circuit means providing an amplitude de- erative to generate said second carrier, said oscillator
modulated response-actuating signal having audio fre- 35 means including a parallel-resonant inductal,ce-capaci-
quency components in accordance with said interrogator tance transmit coil, a transistor having a collector, an
signals; coding means coupled to. said circuit means for emitter and a base electrode, a parallel rccistance-capaci-
transmitting only selected ones of said audio frequency tance network coupled to said base electrode, an induc-
interrogator signals of said response 'actuating signal tance inter-coupling one end of said transmit coil with
and providing thereby a coded response-actuating signal; 40 said network, said collector electrode being connected to
and oscillator means coupled to said coding means and the other side of said transmit coil, said coded response-
solely powered by said coded response-actuating signal . actuating signal being applied to said emitter electrode
for generating a second radio frequency carrier having and one end of said transmit coil.
a frequency different from that of said first carrier and 16. A passive responder unit adapted to be excited by
being modulated by the interrogator signals transmitted 45 a first radio frequency carrier having a plurality of in-
by said coding means. terrogator signals rodulated thereon and for generating
12. Apparatus according to claim 10 in which said ' a second radio frequency carrier having only certain ones
first tuned circuit means includes a resonant pick-up coil of said plurality of interrogator signals modulated there-
inductance and a capacitance; in which said response- on. said responder unit comprising: a tuned circuit hav-
actuating signal also contains a direct component; and 50 ing a resonance frequency corresponding to said -first
to which said second turned circuit means includes an carrier; detector means coupled to said tuned circuit
oscillator means for providing said second radio frequency for providing a response-actuating signal having a recti-
carrier, said coded respcase-actuating :.ignal being con- fled carrier -mporent and a plurality of alternating our-
netted to said oscillator means, whereby said second car- rent components core-ponding -so--said inteTrrrg~ZiSz_6isL
rier is modulated by the audio components of said coded 55 gals; coding means including tuned circuits -responsive
response-actuating signal. to said response-actuating signal for transmitting only
13. Apparatus according to claim 10 in which solely seT lected ones of said plurality of interrogator signals
said coded response-actuating signal provides power to - therethrough and operative to suppress others of said
said second tuned circuit means. interrogator signals, thereby to provide a coded response-
14. A coded responder unit comprising: a parallel- G0 actuating signal having alternating current components
resonant inductance-capacitance pick-up coil excitable in accordance with said selected ones of said interrogator -
with a first, radio frequency carrier having a frequency in signala; and oscillator means responsive to said coded re-
accordance with the resonance fregt_cncy of said pick- sponse actuating signal and operative to generate said
up coil and being.meduhted with a plurality of interro- second carrier, said ceded response-actuating signal pro-
gator signals; carrier demodulator means coupled across 65 victing the see po:ccr to said oscillator nteans.
said pick-up coil to provide a response-actuating signal 17. A sigca:iing sy::em for identifying passive coded
having a direct voltage cornpanent- commensurate with responders with an interrogator, said signalling system
the magnitude of said first carrier and alternating voltage Comprising: interrogator ::ansntit means for producing a
Comnenents commrncnraTP ,.?;0, if,.. f--....:,.- ,.c
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
 Approved For Release 2009/04/10: CIA-RDP81 0012OR000100010003-3
3,054,100
demodulation means coupled to s.;1 responder pick-up
means and operative to demodulate said first carrier and
to provide a response-actuating'signal having a rectified
first carrier component and auda conipoirents corre-
sponding to said audio frequency attcrrogotor signals;
responder coding means coupled to said responder de-
modulation means uperttiv; to trm z lit said rectified first
carrier component and selected oa of said audio com-
ponents and thereby to provide a digitally coded re-
sponse-actuating si_rnrl having said rectified first carrier
component modulated with said ,elected studio couipo-
nents which identify said respondci uniquely, each re-
sponder transmitting a different selection. of audio com-
ponents; responder oscillating means coupled to said
coding means for generating a scecod radio frequency
carrier having said selected audio conipoilents modulated
thereon, said digitally coded response-actuating signal
furnishing the sole power to said oscillatin g means; in-
terrogator pick-up means excitable by said modulated
second carrier; interrogator deniodtalatioit means coupled
modulate said second carrier and to provide a second
rectified caner component and at-No components corre,
sponding to said selected audio frequency interrogator
signals; interrogator signal discriminating means having
a plurality of channels coupled to said ihterrog'ator de-
modulation means, each one of said channels being se-
]ectively responsive to a diUvrent one of said audio com-
ponents and being operative; to provide an output voltage
for each of. the 'audio components modulated on said
second carrier; and a plural stage register means re-
sponsivc to said output voltages, each of said channels
being coupled to a different stage of said register to pro-
vide an indication of the presence or absence of said
output voltages.
18: A signalling systent in accordance with claim 17
including a data link transmissio,t system having a data
link transmitter responsive to said output voltages and
operative to sequentially sample each of said register
stages and encode a third radio frequency carrier in ac-
cordance with the s'at. of said stages, said transmission
system also including a data link receiver means respon-
sive to said third carrier and operative to decode said
third carrier to derive an iadicatioaa of the state of each
of said. stages.
19. A railroad signalling system for sequentially iden-
tifrying a plurality of adjacent passive coded responders
located upon the tracks of a railroad network by means
of an interrogator located upon a railroad vehicle, each
responder being identified when, said railroad vehicle
is approximately at a selected minirmim distance there-
from, said signalling system comprising: an interrogator
including a transmit means for generating a first radio
frequency carrier modulated with a plurality of audio
frequency interrogator si-nals, a receive means for re-
ceiving and demodulating a second radio frequency car-
of said interrogator signa!s theiethrough each responder
including a coding means transmitting a different selected
combination of audio components, and oscillator means
coupled to said coding means and powered by said trans-
5 mitred rectified carrier component and operative to prOvid--
said second carrier, said transraiaed audio components be-
ing operative to moltmlate said second carrier with said se-
lec.icd combination of interrogator signals. -
20. A signalling system for identifying passive coded
10 responders with an interro Bator. said system ccmprisir^:
interrogator transmit means for providing a first radio
frequency carrier having a plurality of audio frequency
interrogator signals modulated thereon; at least one pas-
sive responder responsive to said first radio frequency
career and operative to provide, in response thereto a
second rea~ frequency carrier having only selected ones
of said plurality of interrogator signals modulated there-
on; interrogator pick-up means associated with said in-
terrogator transmit means and excitable by said modu-
lated second carrier; interrogator demodu:ation means
coupled to said interrogator pick-up means and operative
to demodulate said second carrier and to protide a rec-
tified carrier component and audio component: corre-
spou..ting_ to the frequencies, of said selected interrogator
signals; audio frequency discriminating and detecting
means including a plurality of frequency sensitive chan-
nel each 'tuned to a different one of said interrogator
signs s, each one of said channels being s:.lectively re-
sponsive to a different one of said audio components and
operative to provide an eutpat voltage upon application
of an :.udio component to which it is tuned; and plural
stage register means, each stage being set by a different
one of said output vcllagcs to provide an indication of
said selected interrogator signals.
21. A signalling system for identifying passive coded
responders by means of an interrogator and comprising:
interrogator transmit means including automatic gain
control means responsive to a control voltage for provid-
ing an anipli tit de-controlled first radio frequency carrier
leaving a plurality of audio frequency interrogator signals
med.aated thereon; at least one passive responder ex-.
citable by said first carrier and operative to provide, in
response thereto, a second radio `requency carrier having
? only selected ones of said plurality of interrogator signals
45 modulated thereon, said interrogator trans-nit means and
said responder being capable of relative motion in re-
spect to one another so as to vary the degree of electro-
ri;agnetic coupling therebetween; interrogator pick-tip
means for receiving said modulated second carrier; in-
50 terrogator demodulation means coupled to said iriteno-
gator pick-tip means and op: rative to demodulate said
second carrier to derive said control voltage commen-
surate with the rectified carrier comp or.e,t of said accord
carrier and audio comp or,ents corresponding to said.se-
5? leered interrogator signals; `-terrogator signal discrim-
inating and detecting weans having a plurality of fre-
quency sensitive channels each selectively responsive to
rier modulated with a selected ccnbinaticn of said audio a different one of said. audio components and operative
frequency interrogator signals, art audio frequency dis- to provide an output voltage upon application of an
criminating means coupled to said receive means and op- 60 audio component of its individual frequency.
erative to ?prov`.de a separate output voltage for each 22. A signalling system in -ccordance with claim 21
interrogator signal included within said selected com- having a gain; r.1m interposed between said i,terro-
bination, and a multi-stage register, each stage-being Bator deraodu!atien means and said interrogator signal
associated with and responsive to a different one of said lliscrirninating means, said gating means being responsive
output voltages for providing an indication of said in- fir tr, a gat- control signal and bear= operative to transmit
terrogator signals included within aid selected con:bina- said -audio componen:s to said signal discriminating
Lion; and a plurality of responders, ereh responder in- means upon the occurrence of said gate control signal,
eluding a pick-up means for rece vin_ and demodulating and gate control signal means responsive to said rectified
said modulated first carrier to prvriJe? a response-actu- 70 carrier component of said second carrier and ope-alive
ator signal having a rectified carrierecmpor.ent and audio to provide said gate control signal when said rectified
components in accordance with said plurality of interro-. carrier component reaches a predetermined magnitude.
garor signals, a coding means coaipled to said p'ck-up 23. A signalling system in accordance with claim 21
means transmitting said reclified carrier.component and wherein said interrogator transmit means includes a con-
audio eomnnnrn tc rnrrnn,snrl i,i tin:. c.,+l, .,l rnnt h:nnr:nn n trnl vnLonn ?~~~- --'" rectified
Approved For Release 2009/04/10: CIA-RDP81-00120R000100010003-3
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3
the nia_uitude of said rectified carrier component with
a rcfere ce voltage to der; e said control voltage.
21
l
i
c
a
m
i
h
.
ance s
d
A signalling system in accor
24
resp
e
a rect
. wherein said interrogator includes a multi-stage register g terrogator response signal including said selected tnter-
raar:as. each stage of said register being: associated with rogator signals: interrogator signal discriminator means
a different output terminal associated with each
havin
g
ng re-
e
b
i
erts and b
di
-
i
cda pon
d au
o
f sa
a diticrent one o sporsive to a coding voltage difference sign,,!, and a' one of said plurality of interrogator signals for unscram-
plurality of comparing means, cacti comparing means tiling said composite interrogator response signal, said
discriminator means be;:ig responsive to said composite
being responsive to a different coding valtace for corn- 10 -
paring the magnitude of said coding voltage with a further innterrogator response signal and operative to provide re-
reference voltage and being operative to derive said cod- sponge output signals on those of said output terminals
ing voltage difference signal. which are associated with said selected interrogator sig-?
25. A signalling system in accordance with claim 24 nals; a plurality of detector means each responsive to a
wherein each stage of said multi-stage register mean, is 15 different one of said response output signals and op-.:a-
responsive to a reset pulse for clearing said rcg;sicr, and tivc to derive response output voitu~es indicativz of raid
reset-pulse means responsive to said rectified carrier ceta_ selected interrogator s gnats received by said receive
ponent of said second carrier and providing said reset means; and comparing means responsive to said rectified
pulse when said rectified carrier component suffers a pre- response carrier voltage for comparing said rectified re-
determined change of magnitude. 20 sponse carrier voltage with a reference voltage and opera-
26. An ir.;crrogator.responder system comprising: in- tive to provide said automatic gain control difference
automatic gain con- voltage
ludin
g
in
c
t means
i
terrogator transm
trot means responsive to an automatic gain control differ-
ence voltage for controlling the amplitude of elcctro-
hiagnetic radiation in the fond of a first radio frequency
carrier having a plurality of interrogatar signals modu-
lated thereon; a passive responder responsive to said
first carrier and operable to provide response electro-
magnetic radiation in the form of a second radio fre-
quency carrier having only selected ones of said plu-
rality of interrogator signals modulated thereon, said
interrogator transmit means and said responder being
capable of relative movement so as to vary the length
and attenuation of the path of said electromagnetic radia-
tion between said interrogator transmit means and said
responder; a' receiy_e means associated with said inter
magnetic radiation from .s_,J responder 0510 LU
onse carrier voltage and a composite in-'
ifi
d
References Cited in the file of this patent
1;JNLTED STATES PATENTS
2,000,130
Espenschied et al. -------- May 7,
1935
2,369,662
Dceoraine -------------- Feb. 20,
1945
2,542,803
Evans ---------------- Feb. 20,
1951
2,607,004
Harris ----------------- Aug. 12,
1952
2,664,554
Doremus -------------- Dec. 29,
19.53
2.679,043
Lipkin ---------------- May 18,
1954
2,818,732
Bennett ----------------? Jan. 7,
1958
2,841,700
Hsllden ---------------- July 1,
1958
2,851,592
Webster --------------- Sept. 9,
1958
3,018,475
Kleist et al.- ------------ Jan. 23,
1962
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010003-3