GROUND RADIO BULLETIN NO. 24 - March 30, 1950 COMMS. DEPT. L.A.D.
TMC-T RELAY RESISTANCE
In Fault Shaker bulletin #8 we stated that the plug-in relays used in the TMC-T are supplied by two vendors, Clare Relay Company and American Automatic Electric Company. Further tests show that the quick-acting (AQA) relay of both companies have a coil resistance of 300 ohms and are interchangeable. The stepping relays of both companies have a coil resistance of 12 ohms and are also interchangeable.
The Clare ASR (slow-release) relay winding has a resistance of 75 ohms and the American Automatic ASR relay has a resistance of 35 ohms. The TMC-T uses two ASR relays as a matched pair. If these two relays (241 and 242) both have the same coil resistance (75 ohms or 35 ohms) operation will be normal. If relay 242 has a 75 ohm coil, then relay 241 may have a 35 ohm or 75 ohm coil for normal operation. If, however, relay 242 has a 35 ohm coil and relay 241 has a 75 ohm coil, the proper relay sequence will not take place. In other words, when ASR relays of different coil resistance are used, the relay with the highest resistance must be in the 242 position. This is the relay adjacent to the voltage selector block.
PAA PART NUMBER
The catalog section is now in the process of changing a number of radio item PAA part numbers. This will affect all radio item part numbers that are not now in the nine thousand class series. (The first four digits are the class numbers).
As soon as these changes are complete, we will issue equipment parts lists and spare parts kits lists containing the new numbers.
FORM 9211-2107
