|The Teletype Signal Distortion Test Set (Code
Disc Operated with Stroboscope, see above) described herein, is a motor
driven unit arranged to be used for any of the following purposes:
- To transmit signals for testing Teletype start-stop printing
telegraph circuits, and checking the efficiency of Teletype startstop
selectors. These signals are a repetition of any of the following test
signals: TEST MESSAGE, R, Y, T, O, M, V, LETTERS, or BLANK OR CODE LENGTH
MARKING IMPULSE, either undistorted or with controlled degree of
distortion up to approximately 100 per cent.
- To measure accurately, through use of the applicable test set, the
impulse lengths of five level code signals originating from an external
transmitting unit. Synchronous motors with identical gear reductions on
each unit operating on the same source of power are necessary for accuracy
because the transmitting unit and the test set must be kept in exact phase
relation. If one of the units is equipped with a governed motor, a slight
speed variation will cause a wavering of the impulse lengths as viewed on
the stroboscope, making them difficult to measure accurately.
- To check the operation of relays or start-stop regenerative
repeaters in a local circuit. When using the test set in this manner,
transmitted signals from the test set operate the relay or regenerative
repeater being tested, and these signals in turn are routed to the test
set stroboscope for observation.
Distortion produced in the transmitted signals may be any of the
- MARKING BIAS, which advances the beginning of each marking impulse
with respect to the beginning of the character cycle.
- SPACING BIAS, which delays the beginning of each marking impulse.
- (3) MARKING END DISTORTION, which delays the end of each marking
- (4) SPACING END DISTORTION, which advances the end of each marking