Circuit B.

Lesson 3/Learning Event 6

c. Circuit B.

(1) The teletypewriter keyboard (TT 1 KYBD) sends 60-ma neutral

telegraph signals toward teletypewriter printer (TT 2 PRTR), which uses

20-ma neutral signals. Relay B receives 60-ma signals and repeats them as

20-ma signals.

(2) Ground or battery is applied to TT 1 KYBD, depending on circuit

configuration.

Current flows through the circuit to the REC panel and

jacks.

(3) The bias winding of the relay is energized. Therefore, when there

is not line current (space) the armature will be pulled over to the

spacing contact by the magnetic field set up in the bias winding. A relay

so connected is said to be poled spacing. Contacts of the relay pick up

battery and apply current to the SEND panel and jacks leading to the TT 2

PRTR.

Ground is connected to the other side of the printer.

If the

circuit is arranged for the printer to supply battery, the contact points

of the relay must key to ground.

d. Circuit A. Ground or battery is applied to TT 2 KYBD, depending on

circuit configuration. Current flows through the cable wire to receiving

panel jacks the same as in circuit B, and through the line winding of the

relay.

Contact points of the relay pick up battery, and current flows

through the sending panel jacks, ending ultimately in TT 1 PRTR. If the

printer will apply battery, the contact points of the relay must be

arranged for dry keying to ground.

Figure 3-14 shows the DC jack

circuits in the AN/MSQ-73. Figure 3-15 shows only the circuit A portion

of these jacks. Signals start from the TT 2 KYBD and terminate at the TT

1 PRTR. A relay is used as an interface between the two circuits. Since

line current is 20 ma, bias current is adjusted to one-half this value, or

10 ma.

The volt power supply furnishes telegraph battery; positive is

grounded, and negative goes to the circuit.

The van furnishes battery,

and teletypewriters are grounded. VCDF refers to vertical terminal blocks

on the combined distribution frame.

(1) A plug patched into the REC LINE jack connects tip and ring to the

patched circuit, placing the patched circuit in series with the line.

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