Lesson 3/Learning Event 7
(2) A plug patched into the REC EQUIP jack picks up the line on tip
only, placing the patched circuit on the tip only of the jack.
The DEC
EQUIP jack automatically connects the rest of the loop normally so that
the TT PRTR will not run open.
(3) A plug patched into the LINE MON jack picks up the circuit on tip
only, placing the patched circuit on the tip only of the jack.
(4) A plug patched into the EQUIP MON jack connects tip and ring to the
patched circuit, placing the patched circuit in series with the line.
(5) Jack circuits are wired differently to accommodate circuit wiring.
Notice for example, that the signal enters the SEND LINE jack on ring
while it enters the REC LINE jack on tip.
(6) The CUT key switch applies battery to the teletypewriter while
tests are being performed in the van. Constant applied battery holds the
teletypewriter closed, thus minimizing annoyance to the subscriber while
tests are in progress.
Learning Event 7: ISOLATION RELAYS
A total of 30 isolation relay chassis are included in the AN/MSQ-73.
Each chassis mounts two plug-in relays, one for the send loop and one for
the receive loop. The relays are wired into the loop circuits at the CDF.
A pull handle on the front panel, shown in figure 3-16, allows the relay
chassis to be pulled from its mating socket.
a. Relays.
The relays are wet-contact types (mercury) and are
hermetically sealed. Although the relay is electromechanical, there is no
provision for adjustment.
When a relay is defective, it must either be
returned to depot or discarded. The basis of relay operation is identical
with a polar relay and uses both line (loop) and bias winding.
By
terminal strips at the back of the chassis, the relays can e wired in
desired configurations of neutral to neutral, neutral to polar, polar to
polar, or polar to neutral.
b. Controls. Four screwdriver controls make appearances on the front
panel.
Two control bias current and two control line (loop) current of
the two independent send and receive relays.
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