TM 11-5805-356-34-1
The 1180-Hz signal enters the distant vf interface
while data is being transmitted. To prevent the
network and couples through the distant output
voice signal and data signal from interfering
with each other, Electrical Filter Assembly F-
circuit. (detect). The distant break-in circuit (de-
tect) responds by locking the distant send circuit
2, the F-316/U stops all voice signal frequen-
in the space hold condition. The space hold
cies in the vf telegraph band from entering the
couples through both the distance and local re-
telephone channel and stops all vf telegraph
ceive circuits to the input of the distant and local
frequencies from entering the local telephone
alarm circuits. The alarm circuits respond by pro-
circuit.
ducing an audible tone at their associated loud-
speakers. The distant operator responds by
ceasing to transmit and resetting the distant
2-4. Detailed Block Diagram Analysis,
break-in circuit (detect). With the distant send-
TH-22/TG
ing device idle (in mark hold condition) and the
distant space hold released, the distant vf output
a. Send Circuit. A sending device connected to
is inhibited. When the distant space hold is re-
SEND jack J1 keys the send loop. The resultant
leased, the local alarm ceases to sound informing
voltage signal developed across R19 couples
the local operator that the channel is clear to
carry the higher priority message.
emitter follower A1Q3 to modulator A1CR1-
f. Signaling Circuit. When 2-wire or 4-wire
CR2. The modulator shifts the frequency of os-
metallic telephone channels (landlines) are used
cillator A1Q4 in accordance with the dc tele-
a 20-Hz ringing signal may be utilized. When the
operator activates the signaling circuit, a 20-Hz
goes to 1317.5-Hz for a mark and to 1232.5-Hz
signal is injected into the telephone channel via
for a space. The resultant frequency-shift vf
the vf interface network. The signal will activate
telegraph signal couples through emitter follow-
any 20-Hz ringing device connected to the chan-
er A1Q5, gated amplifier A1Q6, amplifier A1-
nel. It will also be detected by the distant alarm
Q7, an attenuator, BOOST switch S6, output
circuit and produce an audible tone at the as-
sociated loud speaker. The 20-Hz signal will not
below) to the telephone channel terminated at
transverse radio telephone or other carrier chan-
binding posts E3E4 or E5-E6. The vf output
nels. For this situation the signaling circuit is
bypasses the attenuator when BOOST switch S6
conditioned to lock the send circuits in space
is operated.
hold when the signaling circuit is activated. The
b. Carrier Suppression Circuit. Delay amplifier
space hold signal is able to transverse any tele-
A2Q14 monitors the send loop via S3-1-2.
phone channel and activate the distant alarm cir-
Should transmission cease and the loop remain
cuit.
at mark hold for 2 seconds or more A2Q14 pro-
g. Threshold Circuit. The threshold circuit
duces an output level that couples through AND
locks the output of the receive circuit in, mark
gate A2Q12-Q13 to inhibit the vf output of the
hold whenever the vf input signal amplitude
send circuit. The gate is enabled by the output
drops below a predetermined level. This function
prevents noise in an idle telephone channel from
5 (set to 2W). Note that if S5 is set to other than
keying the receiving device.
2W the carrier suppression circuit is thus dis-
h. Power Supply Circuit. The TH-22/TG con-
abled. When the first space element occurs each
tains an internal power supply. Input power
time transmission is initiated, A2Q14 releases the
may be either 230 vac, 115 vac or 26 vdc. In
inhibit. The first space element is not distorted
any case two output voltages result: +18 volts
during transmission because A1Q1 and A1Q2
store it long enough for the carrier suppression
volts (5v) to provide internal loop battery.
circuit to release the inhibit. MODE ONE-
MODE TWO switch S10 selects two different
2-3. Simplified Block Diagram Analysis,
delay times for A1Q1 and A1Q2 to accommodate
F-316/U
different transmission rates.
c. Receive Circuit. The incoming vf telegraph
Since the vf telegraph signal occupies only a
signal couples from the telephone channel, ter-
small portion (1317 :5-1232.5 Hz) of the tele-
minated at binding posts E5-E6, through the vf
phone channel band (300-3000 Hz) the channel
interface network (e below), input transformer