Chapter 4 FUNCTIONING OF EQUIPMENT

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-

paragraphs 5-2 through 5-24. Familiarity with the

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

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-

(fig. 8-4)

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

(fig. 8-4)

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