TM 11-5805-424-15/NAVELEX 0967-220-9013/TO 31W2-2G-41
CHAPTER 5
FUNCTIONING OF EQUIPMENT
Section I. BLOCK DIAGRAM ANALYSIS
5-1. General
(1) If the input send data to the MD-674(P)/G is
lost, the input interface amplifier provides a
The purpose, operation, and interoperation of
steady voltage to the no-transition alarm sensor,
the various circuits in this equipment are explained in
which consequently applies a voltage to the 5-
second delay, actuating the delay circuits. If no
equipment, how it works, and why it works that way are
data transitions occur within 5 seconds (or
valuable tools for troubleshooting the equipment rapidly
longer), the common alarm circuitry provides a
and effectively. Circuits of the MD-674(P)/G fall into
ground to light the ALARM indicator lamp. The
three basic groups: send, receive, and timing. The send
5-second
delay
contains
a
control
circuits convert binary input data, or telegraph (order-
(TRANSITION ALARM TIME TRANSMIT) for
wire operation), into a fsk signal suitable for
fine adjustment of the delay circuits. When the
transmission; mark and space frequencies are
input data transitions are restored, removal of
determined by the type of MX-73(*)/G used. The
the voltage applied to the 5-second delay
receive circuits convert fsk input data to either binary or
removes the ground from the ALARM lamp
teletypewriter data, and also provide for regeneration
which extinguishes the lamp.
and retiming of the received input signals. The timing
circuits supply timing signals necessary for the MD-
(2) If the send carrier signal is not applied to the
674(P)/G and for external transmitting and receiving
output amplifier (fsk mark and space
equipment.
frequencies), the failure is detected by the loss-
of-carrier alarm sensor, which then provides an
5-2. Send Circuits
activating voltage to the 2-second delay. If the
carrier signal is lost for at least 2 seconds, the 2-
second delay output causes the common alarm
circuitry to light the ALARM indicator lamp. The
a. Send Data. When set to DATA, the INPUT
XMIT CARRIER ALARM THRESHOLD control
SELECT switch passes the send data signal or order-
sets the minimum amplitude requirements of the
wire signal from the ORDER WIRE SEND jack to the
carrier signal; any signal below this set level
input interface amplifier, which shapes the input data
causes an alarm 2 seconds after the condition
signal and applies it to the tone oscillator control.
persists. When the level is restored to normal,
Depending on the, sense of the input data, the tone
the activating voltage is removed from the
oscillator control enables either the mark oscillator or
2second delay, which removes ground from the
the space oscillator. The mark and space output
ALARM lamp, extinguishing the lamp.
frequencies are divided by an appropriate binary divider
to the correct channel mark and space frequencies. The
5-3. Receive Circuits
two frequencies (fsk signal) are then applied through the
transmit filter.
which removes any undesired
frequencies, to the output amplifier.
The output
amplifier provides for an output level adjustment of the
a. Receive Data. Of the receive fsk data applied
output fsk signals, which are then supplied to the
through the input amplifier, only the proper channel
external transmitting equipment.
b. Send Alarms.
Change 3 5-1
