Figure 57. Record output amplifier, Facsimile Transceiver TT-1(*)/TXC-1.
76. Automatic Stop Circuit (End-of-Copy
through the primary of the stylus trans-
former T3 and the selector switch. In
Facsimile Transceiver TT-1E/TXC-1,
resistor R106, and capacitor C68 are
An automatic stop circuit is incorporated in
added in series across the selector switch.
One aide of the secondary is grounded
the amplified facsimile signal to ground and to
and the stylus is connected to the high
stop the synchronous motor when the drum reaches
side through an rf suppressor composed
the end of its travel. The circuit operates in all
of R73, R91, and C44. This suppressor
positions of the selector switch and has a locking
feature when in the TRANSMIT, RECORD
spark. The audio output voltage causes
DIRECT, or RECORD PHOTO position. The
a spark between the stylus and the
stop is intended to prevent unnecessary wear of the
grounded metal drum of the transceiver,
half nut threads if the machine is left unattended
burning the white covering from the
at the end of a transmission. It prevents marring
black recording paper.
of the recorded copy by the stylus should the
operator move the drum to the right at the com-
(3) Cathode circuit. In normal operation of
pletion of a transmission while the selector switch
stage V14, the cathode is connected di-
is in the RECORD DIRECT position and the
rectly to ground through contacts of the
incoming signal is still on. The circuit consists of
phasing switch. This permits normal
limit switch S8 which is operated by the drum
zero-bias operation of the Class B stage.
when it reaches the end of its travel. It also con-
During phasing operations, however, re-
sists of relay K1 which is energized by 115 volts
sistor R72 is connected into the cathode
dc obtained by passing regulated dc voltage
circuit of V14 and becomes a coupling
(RB+) through dropping resistors R109 and
resistor between stages V14 and V15.
a. When the transceiver ia operated in the
transferred from the output of V14 to the
TRANSMIT position and the drum reaches the
input of V15.