Quote Originally Posted by WU9G View Post
WHOOOSH!

That's the sound of this thread going WAY over my head.
GPIB is an acronym for "General Purpose Instrument Bus". It's IEEE 488.2, and specifies a data-transfer standard by which laboratory instrumentation can be controlled.

A lot of the test equipment produced in the pre-USB/Ethernet days has a GPIB connector to facilitate programmatic control or step execution...data gathering and so forth.

Control logic is state-driven, meaning one piece of gear can wait on another to acknowledge an operation before it proceeds with a task.

Example: I have a Tek 5000-series plugin with a 50M40 relay card. I'm going to use one of the lines to switch the PTT circuit of a transceiver under test. Immediately after the relay controller signals closure, the main controller program commands a signal generator to generate a single-tone (1KHz) sine wave of 2.5mV amplitude...which is applied to the rig's Mic In connector.

Another instrument is then commanded to make power readings and yet another is commanded to study the RF output waveform. Should said waveform show signs of distortion (or other 'fail' criteria) the signal generator cuts its output and the relay card opens the PTT circuit, putting the device under test back into receive mode.

You've used an ATM before, right? They're all state-driven.