Lesson 2/Learning Event 3
b. Tip-Only Jack.
A tip-only jack places the current on the tip of
the patch cord only. The circuit must be completed through the tip of the
patch cord to another tip-only jack. This type of jack is useful when the
technical controller must "lift" an item of equipment or a segment of a
circuit out from the remainder of the circuit.
Such a jack type is
usually associated with a single-wire ground-return telegraph circuit. A
tip-only jack may contain multiple contacts so that the remainder of the
circuit is closed at the time that the tip of the patch cord lifts the
portion of the circuit in question.
c. Current Adjustment.
Every telegraph circuit is equipped with a
current-controlling device, usually a rheostat or potentiometer.
Every
time a patch cord is inserted or removed, the technical controller must
check circuit current and, if necessary, readjust the current to the
required value. Transistor devices are available to automatically insert
the right value of resistance to maintain current at a constant value.
d. Telegraph Distortion Check. The technical controller should use a
digital distortion analyzer on a daily basis to check each circuit passing
miscellaneous signals to determine the amount of distortion that exists.
This is a normal daily operating routine, and is especially important in
activating new circuits or patching existing circuits.
The technical
controller must know the amount of distortion so that he can predict
circuit performance. If he fails to perform the distortion test, he may
find himself in difficulty at a later time when the circuit fails
completely.
If the circuits contain excessive amount of telegraph
distortion, he should refuse to accept them until the trouble has been
cleared.
He can provide temporary service by rerouting traffic over
circuits free from distortion.
e. Patch Cords.
Technical controllers must handle patch cords with
care. Never pull on the cord itself; pull only on the plug. A cord found
to be defective must immediately be removed from the area so as to prevent
its possible use by mistake. Further, patch cord plugs must be inserted
in and removed from jacks with a quick deliberate motion.
Moreover, a
cord should never be left dangling; either both ends of the cord should be
inserted in jacks or the cord removed completely. A cord dangling from a
DC patch panel is a shock hazard, and accidental contact of the exposed
plug with ground can result in blown fuses.
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