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
(2) Ground or battery is applied to TT 1 KYBD, depending on circuit
Current flows through the circuit to the REC panel and
(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
Ground is connected to the other side of the printer.
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
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
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.