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The 31/53 Instrumentation system consisted of a special TM-500 plug-in module called the 153 Interface, a special TM-500 chassis that contained a power supply for the TM 500 plug-in instrumentation modules and a backplane for communications between the 153 interface and the instrument modules. Lastly up to two modified (Option 4) TM-500 instrument plug-ins, and a cable that connected the 153 interface to the I/O connector on the rear panel of the Tek 21 or Tek 31 calculator.
The 31/53 Instrumentation System was introduced in March, 1974
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