Ground: voltage level

[Nigel Goodwin]

Nigel
this is a good point, can you tell me where TVS's are convenient?
I am using an axial TVS. I guess they protect inputs and outputs pins from power noise or signal noise. There are others TVS in my circuit, one in the reset pin, another between Vdd and Vss and some others in some inputs pins where the circuit is closed by a push botton.

They are simply to try and limit the voltage, probably useful on any input (signal or power) which might have high voltage spikes on it?.

I can't say I've ever had occasion to use one!.