TS-652/GG - Teletype DXD200 (Bell 1A) Test Set - Restoration Project

Just Getting Started!  

Video of this DXD200 unit in operation

spinning disk stroboscope/distributor
tty-test-bell1a-5225.JPG (1690049 bytes)

tty-test-bell1a-5230.JPG (1917142 bytes)
Cams for "quick brown fox" message
tty-test-bell1a-5231.JPG (2569738 bytes)
stroboscope lamp & distributor brushes
tty-test-bell1a-5232.JPG (2281422 bytes)
Yeah, it will take a little wiring repair!
tty-test-bell1a-5226.JPG (2061271 bytes)

tty-test-bell1a-5227.JPG (1229640 bytes)

Done - not beautiful but no more sparks and arcs......

dxd200-1804-wire.JPG (2114784 bytes)


dxd-spec-01.jpg (348048 bytes) tty-test-bell1a-dwg.jpg (155496 bytes)
Stroboscope display examples - The character begins at the bottom and goes clockwise - Start (spacing - 1 unit), 1, 2, 3, 4, 5, Stop (marking - 1.42 units)
LTRS = Start, M, M, M, M, M, Stop
dxd-trace-04.JPG (3336410 bytes)
Blank = Start, S, S, S, S, S, Stop
dxd-trace-03.JPG (3252310 bytes)
R = Start, S, M, S, M, S, Stop
dxd-trace-01.JPG (3375037 bytes)
Y = Start, M, S, M, S, M, Stop
dxd-trace-02.JPG (3354096 bytes)
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:
  1. 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.
  2. 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.
  3. 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 following types:

  1. MARKING BIAS, which advances the beginning of each marking impulse with respect to the beginning of the character cycle.
  2. SPACING BIAS, which delays the beginning of each marking impulse.
  3. (3) MARKING END DISTORTION, which delays the end of each marking impulse.
  4. (4) SPACING END DISTORTION, which advances the end of each marking impulse.