SINGLE-CHANNEL APPARATUS FOR HIGH-FREQUENCY TELEPHONY

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600260591-7
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 9
• Document Creation Date: December 22, 2016
• Document Release Date: August 4, 2011
• Sequence Number: 591
• Publication Date: November 14, 1949
• Content Type: REPORT

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This new eiagle-channel apparatus for high-frequency telepnony is
mainly ir_tended for the consolidation of steel circuits but can also be
utilized for the consolidation of coppe- circuits.
la a steel circuit with conductors a nm in diameter, distances of 20
cm between conduotome, and under sleet conditions (8 = 25 mm), the appa-
ratus guarantees a atee.ly telephone contact at a distance of 80 loo between
intermediate stational and 90 kd between a ttu?Idnal and '_utermadlatu eta-
tim, or two terminal stat!ons. In A copper circuit the distance between
any two neighboring stati-as can be. brought up to 350 kr-.
A set of aingle-channel apparatue (terminal or intermediates) consists
of equipment essential for receiving one high-frequency and one low-fre-
quency channel. All line and bziancil-g filters vbich are necessary for
joint operation in both channels are assembled on a rack cannon to all of
the equipment.
The voice-frequency channel has a frequency spectrum of 300 - 2,000
ape; the high-frequency channels transmit 2,600 - 5,100 cps in direction
A -B, and 6,700 - 9,200 cps in direction B-A. The high-frequency-channel
circuit does not transmit the carrier frequency currents to the line.
These currents are utilized as control-frequency currents. The control-
frequency in direction A-B Is 5,400 cps, in direction B-A, 6,400 cps.
Thus, to the line from. Station A, side-frequenc. currents of 2;400 -
5,100 cps and the control-frequency current of 5,400 cps are transmitted;
from station L, aide-frequwtcy currents of 6,700 - 9,200 cps, and the coa-
isol-f egeency.current of 6,400 cps.
COUNTRY US56
SUBJECT Scientific - Telecommunications
HOW
PUBLISHED Monthly periodical
WHERE
PUBLISHED Moscov
DATE
PUBLISHED Apr 1948
LANGUAGE Russian
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DATE DST./'/Nov 1949
No. OF PAGES 9
SUPPLEMENT TO
REPORT ISO.
THIS IS UNEVALUATED INFORMATION
SOURCE Vestnik Svyazi - E1ek=t_ ', No 4, 1948.
Information requested.>
figuree are appended]
CLASSIFICATION cON!'IIIENTIAl?.t
CENTRAL INTELLIGENCE AGENCY RESORT
INFORMATION FROM
SIHGIB-CHANNEL APPARATUS ROR H?GB-FRIQUENCY TSIJPBONY
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- 1 -
C CI TIAL CIVIENTIAL
DISTRIBUTION . .
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CONFI M.. L
device, intended for dispatching calla to the line and to the switchbcxird,
for (1) conversation control of subscribers, (2) negotiations with sub-
scribers, and (3) transmission and reception of currents of measured fre-
quencies; a voice-frequency current generator, used for providing the line
with currents of 400, 1,000, and 2,000 cps; a level indicator with an input
resistance of 600 and 5,000 ohms for measuring the level of cransmission
within limits of -2 t 3.3 neper; two mslllammeters, to check the value of
the tube plate currents; teat jacks, serving to isolate separate circuits
of the apparatus for testing and for replacing defective circuits; a set
of cores with plugs for switching and testing purposes; a sot of connecting
lines for transferring separate circuits to the measuring section of the
line-switching room for testing purposes, and for replacing circuits with
similae ones distributed on other panels; a milliammeter for measuring con-
trol-frequency current; and a 24/220 volt voltmeter. An intermediate sta-
tion set has equipment Identical with that of a terminal station, with the
saception of. a voice-frequency generator.
The entire apparatus in every station, as listed, is installed on one
rack. Separate units are distribut$.an two sides of the frame, with the
regulators and jacks placed on the front panels, while tl4te tubes are covered.
The apparatus is equipygd with tubes of the metalli eeriea 6J7 and W.
It is fed frog the ordinary station bdtteri.ea of=2220 -2 .pnd 24 volte.
The single-channel apparatus has automatic amplification regulation,
based on resistance changes of he tube of a special pre-amplifier, with
changes in the grid bias cf Ltiis tube. The changing bide results from a
special selective amplifier which amplifies only the control-freauene,v cur-
rent.
The control-frequency currant proceeds from the output of the common
amplifier to the input of the selective amplifier. which has a high input
resistance. It is amplified here, and then rectified through a cuprous-
oxide rectifier. The rectified current is measured with a millimeter.
By means of a potentiometer, connected to the grid of the amplifier tube of
the selective amplifier, the magnitude of the rectified current is ester afied
equal to 0.3 riiiliempere.
In order to obtain a sharper characterietic of amplification change
relative to change in control-frequency ctirrent, the difference between two
steady voltages is placed an the grid of the tube of the special pre-ampli-
fier. This voltage diff9rance consists of a positive constant voltage of
16 vole, from e, spniiel circuit, which is stabilized by a neon tube fed
from the plate batter; (the stabilisation is needed for maintaining a con-
stant value of positive voltage during f luctuati o:s in the plate voltage),
and of a negative voltage recei-a.i frr. the ceerl!iod and rectified current
of the control frequency.
Because of this connection, the grid biac on the tube of the special
pre-amplifier, with a fluctuation of the level of the control frequency
voltage of t 0.1 neper, ch u es in the limits from -5 v to -1 v. Thus,
the stage gives either amplification or attenuation. The amplification
changes are sufficient to compensate for the attenc tIcn changes on the
line, depending on weather conditions: from 'winter, dry" to "moderate
sleet."
coNFIDEA1IA1
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quency characteristic of the amplitude distortions in the regulating stage.
Thie Is possible through connection of an L9 resonant circuit in a feedback
circuit of the special pre-amplifier tuba.
With Blight attenuation on the line, the bias on the grid of the pre-
amplifier increases. In comparison with the input resistance of the IC
circuit, the internal resistance of the tube increases also. Consequently,
the current feedback, through decrease of the alternating voltage on the I.
circuit, drops abruptly. Therefore, practically, one can call the frequency
characteristic of the stage linear.
If the attenuation on the line increases, the bias on the grid of the
tube decreases. The tube starts to work on the linear portion of the char-
acteristic, its resistance sharply diminishes, and becomes proportional to
the resistance of the IC circuit. Consequently, the resistance of the LC
circuit becomes significant in comparison to the resistance of the tube and
the influence of the feedback on the amplification of the tube increases.
The parameters of the LC circuit are selected in such a way that high
frequencies arA amplified more by the pre-amplifier than the low frequencies.
As a result, the supplementary frequency distortions and line attenuation are
compensated for through the distortion and increase of amplification of the
special pre-amplifier.
In order to get this adjustment it is necessary, during winter weather,
'to set the plate current of the tube of the pre-amplifier within the limits
of 0.1 - 0.2 ma, changing the negative bias on the grid of the tube by a
potentiometer.
In case of a defect in the automatic adjustment of the amplification,
a provision is made to change over to manual adjustment, In which a filament
battery is used for the negative displacement of the characteristic.
A characteristic of the automatic amplification regulation is the large
grid-plate transconductance; It Is therefore not permissible for the apparatus
to transmit large amplitudes of side frequency currents. At amplitudes of
more than + 2.5 nepers, the amplitude characteristic at the output of the high-
frequency amplifier levels off. Consequently, the level of the control fre-
quency diminishes, the amplification increases, and the bead of the ampli.trda
characteristic becomes even larger. In the course of the above process, the
automatic regulation stops working, the amplification rises up to the maximum
value and the coupling starts to vibrate. Therefore, it is necessary, when
connecting the apparatus for manual adjustment, to measure the amplitude ?hrsr-
acteristic of the residual attenuation.
In order to weaken the described effects, the apparatus has ar. amplitude
limiter (Figure 1) consisting of a series and a ehunti.jg arm. Duc to the
joint action of both arms, a steady limiter input resistance is obtained nearly
independent of the amplitude of the incoming voltage.
The limiter is connected in the transmitting section of the terminal sta-
tion between the choke-filter and the modulati.r and has a?threshold limit near
the level-2 nepere. To change the threshold limit it is possible to connect
elongatore either before or after the limiter. By increasing the attenuation
of the elongatere before the limiter and decreasing the attenuation of the
elongatore after the limiter, the threshold limit decrease; with a decrease
in the attenuation of the elongatore connected before the limiter, and with
an increase in the attenuation of the elongators after the limiter, the thres-
hold limit increases.
C0N'IDII TIAL
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of + 2 nepere at the output of the amplifier.
Far controlling the threshold limit a rheostat can be used which
permits changing the voltage applied to the cuprous-oxide rectifier of the
e
-
lateral branch of the amplitude limiter. However, it is not advisable to
change the voltage within wide limits because the input resistance of the
limiter alters greatly during this process.
The installation of a limiter has yet another useful possibility; be-
cause of the limiter the influence of ineufficiently large "clear" attenua-
tion of the condenser filters K-2, 3 weakens considerably. This is of spec-
cial importance in phantom-circuit utilization of the apparatus for a two-
way group telephone coru.ection.
In order to compensate for the formation of amplitude frequency distor-
Lions in the line, quadripole equalizers are employed in the high- and low-
frequency channels. These quadripole equalizers have properties which make
it possible to establish different correction limits by resoldering only the
real resistances, without changing the reactive elements of the quadripole,
even when the apparatus is switched fr . steel. to copper circuits. This
characteristic simplifies considerably the quadripole equalizing schema and
facilitates their manufacture. If the apparatus is working on short sections
of line, additional links are connected to lengthen the line. Every apparatus
has two of these links.
In the feedback circuit of a low-frequency amplifier there are special
circuits which make it possible to regulate the frequency "baracteristics of
the channels in high-frequency regions. T13 regulation makes it possible to
olio illupi'H M1 wa111 {.11C 111(11Gd Vl
0.3 nepor for the whole coupling.
Regulation is also provided in the feedback circuit of the low-frequency
amplifier for changing the frequency characteristic of low frequencies (300
cpn) in the high-frequency channel. In the voice-..frequency channel a 3lmiler
regulation is carried out by means of a condenser, with a shunt resistance,
connected in series with the primary winding of the grid transformer.
Figure 2 shows a skelet u dirgr+Am of the terminal station. The
scheme permits duplex operation, two-wire and four-wire (phantom) transit
connection and a two-way group connection on the high-frequency channel;
also duplex upeiation and two-wire transit connection on the voice-frequency
channel.
The skeleton diagram of an intermediate station is shown on Figure 3.
One can see that the introduction of special equalizers in the intermediate
stations to compensate fx the amplitude distortions of the filters makes
it pooeible to obtain good-quality high-frequency channels. Choke filters,
D-10, which exclude frequencies above 10,000 cps, are set up to protect the
high-frequency channel from influence of other networks.
Figure 4 shows orientation diagrams of equalizers in basic unite of
the terminal rnd intermediate apparatus, connected in a steel circuit at
distances of 80 km, under "dry, winter -200 C" conditions.
Curves of residual attenuations of high- and low-frequency channels
are shown in Figures 5 and 6. The high-frequency channel has a width of
300-2,600 cps, with distortions much lees than the permitted standard; the
audibility Is very good.
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The width of the voice-frequency channel is 300 - 2,000 cps. The
distortions are also minor, but greater than in the high-frequency channel.
The limitation of the higher frequency range diminishes to some extent the
transmission quality. Regulation of this channel is by far more complicated
than the regulation of the high-frequency channel.
Figure ; dopiotd the amplitude characteristics of the high- and voice-
frequency channels. The amplitude characteristic of the high-frequency channel
vac tnJcn while the il,uito- was disconnected. If the limiter is connected, the
curve characteristic changes abruptly, but the influence of the "clear" attenua-
tion of the X-2,3 filters diminishes considerably.
The "clear factor" of channels with the limiter connected fluctuates
between 5 - 6 percent, but diminishes to 1.5 percent without the limiter.
From the curves, illustrated by Figures 8 and o, one can see that during
current variations in the tube of the special pre-amplifier not only does the
amplification of the stage change; but also the amplitude distortions com-
puted to compensate for diEtortiou on an 80-kilometer- long-section of the
steel circuit, in the case of weather change from "winter, dry" to "sleet."
On shorter sectiol1s cf a steel circuit or during operation on a copper cir-
cuit, it is possible to find the most advantageous point with vide regula-
tion Unite by regulating the plate current of the pre-amplifier tube.
Cross-talk attenuation between high- and low-frequency channele exceeds
7.5 nep. However, by sending indaced currant along the voice-frequency channel,
an audible effect is noticeable in the high-frequency channel in the form of
an initial click and a weak background.
Because of its operational characteristics, the apparatus of a single-
channel consolidated system is very flexible and can be serviced completely
without any additional test. equipment. The apparatus is compact and there-
fore can be net up in a smaller space, which is of special importance in
district centers.
Good operational qua.i'es of the apparatus are basic reasons to expert
widespread circulation at jcnctione of regional importance. Mass production
of the apparatus will sharply increase the quality of interregional connec-
tions and the connections of regions with provincial centers.
/figures fnllou.7
C C'7PIfENTIAL
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Figure 2. Skeleton Diagram of the Terminal
. tioa B; DB - differential system, OT9 - tone-call gene:-ntor, BK -
ealanciog circuit, P1V - thoscall receiver, TUAI ?? transit elongator,
FNCh - lov-frequency filter, 4.0 - limiter, M - modulator, PF - band
filter, G - oscillator, UeVCh - high-frequency amplifier, UeNCh - lov-
frequoncy amplifier of the high-frequency chcur al, K - condenser filter,
.a.. IN - line transformer, D - choke filter, LV - line 9qualizer, ARU -
autmatic level regulator, IN - demodulator, BDS - balancing choke-
condenser filter, UdTCh -amplifier for voice-frequency channel, UdI -
alcogatcr.
CONFI1 NTIAL
Vel0l0rkn On', 11 A AL
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CONFIDENTIAL
Figure 3. Skeleton Diagram of an Intermediate Station:
Fier K - condenser filter d2 line transformer, D - choking filter, LV -
line equalizer, ABU - automatic level regulator, BDB - balancing choke-
c'z denser filter, VI - equalizer for the condenser-filters, VD - equalizer
DS - differmtial syretem, BK - balancing circuit, FWb - lou-frequency"
filter, tJeYCh :- high-frequency amplifier, Ue`FCh - voice-frequency ampli-
i r r rr? t?-1 r-v
?44a' +1.4 :70 0 -0.9 -t?Bnepsr
-04 40.1r ro.l CC."t"l pa49
iJ
-2-S, -3.0
?t 3 . eC- n e, c..-
~ - ~ ~~ ~
rcnf lldJ~ - - ri' 31-=i
. Figure 4. Diagram of Bqualize:e:
1 - terminal station B (.Lecelving); 2 - terminal station A (receiving),
3 - terminal stations A and B (transmleeion), 4 - intermediate station
(direction A - B, 5 intermediate station (dlrectice D - A.)
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ZT L (Steel)
50X1-HUM
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Figure j. Curve of Residual Attenuation of the High-Frequency Channel
Figure 6. Cured of Haeidual Attenuation of the Voice-Frequeucy Channel
6
Figure 7. Am ,itade characteristics: 1-characteristic of high
frequency chI -1, 2-characteristic of voice frequency charnel.
IUnimC1 i IRi
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YI n}IV h`. YI
I I A L
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