Switch TENS unit between many channels
I would like to switch the output of a tens unit to 8+ different outputs.
&quot;Max frequency output is 150 Hz.&quot;
&quot;I would probably want to be switching at ~1000 Hz.&quot;

Something is not right here. It seems to me that you think you can use one TENS machine to do the job of eight+ by switching fast enough. I can see a few problems:

You will no longer be applying a 150 Hz signal to the skin. You will be applying a 1 kHz signal modulated at 150 Hz.
The average current will fall to 1/8 of the current in correct use (if everything else goes well).
The TENS unit is probably running a constant current generator circuit. Rapid switching of the load will probably cause havoc with the internal regulation.

Note: SI Units named after a person are capitalised when abreviated and lower-case when spelled out. &quot;V&quot; for volt, &quot;Hz&quot; for hertz, etc.