contact. The bias winding causes the armature to swing to the SPACE contact during each space (no current). The bias
winding and its current, therefore, act as an electrical spring that returns the armature to the SPACE contact. The distance
between the MARK and SPACE contacts and the armature is very small, so the transit time between repeated pulses is
very short.
f. The direction of current flow in the line winding is important. If the current is turned over--that is, if it flows
in a direction to aid the bias winding instead of opposing its effect. The result is that the armature will remain on the
SPACE contact constantly and the receiving teletypewriter will run open.
89.
The Polar Half-Duplex Teletypewriter Circuit.
a. The polar half-duplex circuit uses a teletypewriter and a dc repeater at each end of the line as shown in figure
85. The wire connecting the teletypewriter to the dc repeater is known as loop. The west send relay converts neutral
signals from the west teletypewriter into polar signals which are sent over the line. The east receive relay converts
received polar signals into neutral signals so that receive copy can be printed on the east teletypewriter.
b. When you are transmitting from west to east, signal flow is from the west transmitting contacts in sequence
through the following:
(1) The west selector magnet (which produces home copy).
(2) The current adjust potentiometer.
(3) The line winding and mark (M) or space (S) contact of the send relay.
(4) The current adjust potentiometer at the west repeater.
(5) The line.
(6) The winding and mark (M) or space (S) contact of the east receive relay.
(7) The line winding of the east send relay.
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