Chart Recorder and Its Replacement

Pax Electronica
 

I apologize in advance for this question not being specific to Tektronix. But I think many of you are familiar with what I am about to ask.

In old instruments, the output is often send out to a chart recorder. The signal is typically sent through two connectors, one of them is kept at ground. I suppose the recorder would need special signals for "start recording" and "end recording". Can someone explain how this is done?

Thanks.

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