transformer T2 through switch S1, sec-
(3) The slider on receiving GAIN control R60
tion 4. Secondary No. 1 is connected
connects through S1, section 2, S5, and
through S1 section 4, S5, and S1 section 3
R50 to the grid of first signal amplifier
to LINE JACK J5. Secondary No. 2 is
V10.
connected through S5 and S1 section 1
(4) Tubes V10, V11, and V12 amplify the sig-
to the LINE binding posts.
nal and apply it through switch S1, sec-
tion 4, to the primary of T2. Secondary
(6) The 1,800-cycle signal from the fork unit
No. 1 of T2 is connected through switch
is supplied to the motor amplifier circuit,
S1, section 4, and switch S5 to SPEAKER
and the motor can operate.
JACK J7.
(7) The push-to-talk relay control circuit on
(5) The 1,800-cycle signal from the fork oscil-
the CARBON MIKE jack is closed to
lator unit to the motor amplifier circuit
put the transmitter on the air when a
is grounded through the exciter lamp
radio circuit is used.
and filament transformers, and the syn-
(8) Resistor R98 (in Facsimile Transceivers
chronous motor does not operate.
TT-1B/TXC-1 through TT-1F/TXC-1
(6) Subparagraph (5) above does not apply
only) is disconnected as a shunt across
t o Facsimile Transceivers TT-1D/
R92 and is shunted across the LINE
T X C - 1 , TT-1E/TXC-1, and TT-1F/
JACK terminals.
TXC-1. In these models, the grid of V4
is grounded through S1, section 6, and
the synchronous motor does not operate.
V9, and V25)
(7) The PHONES and RADIO RCVR jacks
(J1 and J2), permanently connected in
The B+ voltage regulator, located in Facsimile
parallel across the primary of T7, pro-
Transceiver TT-1(*)/TXC-1 (figs. 63-65), drops
vide for voice reception when a radio cir-
the 450-volt dc input from the rectifier power unit
cuit is used.
to regulated +250 volts for critical transceiver
b. MON (Monitor position). In this position of
circuits.
the STANDBY-MON-TALK switch, the same
a. Two triode-connectad voltage regulator out-
connections are completed as in the STANDBY
put tubes (V7 and V8, type 7C5) (fig. 63) are
position, except that the 1,800-cycle supply to the
connected in parallel with their plates at +450-
motor amplifier circuit is not grounded, and the
volt potential and their cathodes at +250-volt
motor can operate.
potential. In this way, their plate cathode im-
c. TALK.
pedance forms a variable series dropping resistor
(1) The LINE binding posts are disconnected
to drop the +450 volts to +250 volts. The value
from input transformer T7 and connected
to output transformer T2 (secondary
of this dropping resistor is automatically varied
by varying grid bias of the tubes to provide a
No. 2), through S1, section 1, S5, and
constant output voltage. Tube V9, type 7L7, a
300-ohm dropping resistors R84 and R85,
(2) The LINE jack is disconnected from input
pentode, control voltage amplifier tube amplifies
voltage changes in the +250-volt supply and con-
transformer T7 and is connected to out-
put transformer T2 (secondary No. 1)
trols the grids of regulator tubes V7 and V8. The
through S1, sections 3 and 4, and S5.
gaseous voltage regulator tube (V25) in the cath-
(3) The receiving GAIN control R60 is dis-
ode circuit of V9 provides a constant voltage drop
connected from the first signal amplifier
(approx. 70 volts), serving as a reference level for
V10. No GAIN control is used in the
stabilizing the +250-volt output. This tube is
talking end of the talk-back circuit.
type R1160A or R1160B in Facsimile Trans-
(4) The loudspeaker serves as a microphone
ceivers TT-1/TXC-1 and TT-1A/TXC-1 and
and is connected through SPEAKER
type 5651 in Facsimile Transceivers TT-1B/TXC-
JACK J7, switch S5, switch S1, section
1 through TT-1F/TXC-1. The output voltage
2, and resistor R50 to the grid of the first
may be stabilized anywhere between +240 and
signal amplifier V10.
+255 volts, but once established, it will not vary
(5) Tubes V10, V11, and V12 amplify the
more than 2 volts under normal operating condi-
signal and apply it to the primary of
tions.
