TM 11-5805-356-34-1
FUNCTIONING OF TH-22/TG AND f-316/U EQUIPMENT
Section I. BLOCK DIAGRAM ANALYSIS
c. 4-Wire Half Duplex. If the network is con-
2-1. General
figured to interface with a 4-wire telephone
a. The TH-22/TG is a full duplex telegraph
channel that is to be operated half duplex (radio-
signal converter. Two TH22/TG units provide
telephone channel for example) the normal traf-
the electronics required to establish telegraph
fic receiving device will be available to print out
communications via a telephone channel. The F-
home copy. This function is accomplished by en-
316/U interfaces both a local telephone circuit
abling a home copy circuit that connects the vf
and a TH-22/TG to the same telephone channel
ends of the send and receive circuits together.
to facilitate simultaneous voice and telegraph
Also a remote control closure (CONT) is pro-
vided to enable the radio transmitter during send
b. The simplified block diagram analysis
operation.
d. 2-Wire Half Duplex. With the network con-
formed by the TH-22/TG. Paragraph 2-3 de-
figured to interface with a 2-wire telephone chan-
scribes the function of the F-316/U. The de-
nel, only half duplex operation is possible. It is
tailed block diagram analysis (para 2-4) de-
therefore necessary to remove the send vf carrier
scribes how each major function is accomplished
from the telephone channel while receiving. This
by the TH-22/TG. Section II describes specific
is accomplished by the carrier suppression circuit.
stages of the TH-22/TG on a schermatic diagram
When the sending device ceases to transmit it
basis.
goes to mark hold. The mark hold is detected by
the carrier suppression. circuit which responds by
inhibiting the vf output of the send circuit. Home
TH-22/TG
copy is automatically provided on the normal
traffic receiving device since the line side of the
a. Send and Receive Circuits. The send circuit
output and input transformers are connected in
converts dc telegraph signals to voice frequency
parallel, via the interface network, when it is con-
(vf) frequency-shift telegraph signals (1917.5 Hz
figured for a 2-wire channel. Since the 4WS-
mark, 1222.5 Hz space) suitable for transmission
TEL vf termination is not used with 2-wire tele-
via a telephone channel. The receive circuit con-
phone channels, it is available to connect to a
verts incoming vf telegraph signals to dc tele-
local telephone circuit. At will, the operator can
graph signals. At the vf end the send and re-
configure the vf interface network to connect the
ceive circuits connect through a (vf interface)
local telephone to the 2-wire channel terminated
network that interfaces them with either a 2-wire
at 2W-4WR.
or a 4-wire telephone channel. At the dc end of
e. Break-In Circuit. If during 2-wire opera-
the send circuit, internal loop battery is pro-
ation, the distant station is transmitting and the
vided. At the dc end of the receive circuit either
internal or external loop battery may be utilized.
local station has a higher priority message it is
b. 4-Wire Full Duplex. With the network con-
possible to break-in. The local operator activates
figured to interface with a 4-wire telephone
the local break-in circuit (initiate) which locks
channel, signals may be sent and received simul-
the local send circuit in the 1180-Hz hold condi-
taneously (full duplex). In this case the receiving
tion. The 1180-Hz break-in signal is able to
device is not available to print out home copy.
transverse the channel in spite of the incoming
If home copy is required, provisions are avail-
vf telegraph signal (because the two signals are
able to connect another receiving device in series
with the send loop.
situated at different points on the vf spectrum)
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