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Test Apparatus Disclosure Number: IPCOM000096222D
Original Publication Date: 1963-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 51K

Publishing Venue


Related People

Mandra, RR: AUTHOR [+2]


Telegraph message switching equipment is tested without disturbing telegraph line conditions.

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Test Apparatus

Telegraph message switching equipment is tested without disturbing telegraph line conditions.

A telegraph message switching exchange and distant terminals communicate on a number of telegraph lines by means of telegraph code mark and space element signals. For example, a space element is sent on telegraph line 1 by opening, via data out line 1, a normally closed transmit TMT relay 1. Such generates a no current condition for a normally closed relay at distant terminal 1. When the message switching exchange receives a space element sent by terminal 1 by opening the terminal's telegraph key, the normally closed receive RCV relay 1 is deactivated. This causes a potential +V to be applied to data in line 1 via an Or circuit.

During normal operation, each element transmitted from the exchange by operation of a transmit relay also causes operation of its corresponding receive relay, supplying to the corresponding data in line an echo of the element placed on the telegraph line.

Wrap relays permit a complete test of the transmit and receive relays, and the equipment associated with two data in and two data out line sets, without disturbing conditions on either telegraph line. When the wrap around test switch is closed, telegraph lines 1 and 2 are shunted by an 820 ohm resistor. This permits a flow of current sufficient to hold the relays in the terminals and exchange operated. Potentiometers A and B in terminals 1 and 2, respectively, are used to supply a...