Piper I checked today they could both be turned off and on independently of each other....
Cessna 152 switch just checked this minute
Alt cannot be turned on without it turning the Battery switch half on, ie push the Alt half in and the Battery half goes in too.
Battery can be turned on, on its own without turning the Alt switch half on.
Once Battery half is on Alt can be turned off and on independently as long as battery half remains on.. Two switches built into one item.
Hope that helps
Now on a 172R you have one Avionics Master switch, but that has 2 independent switch halves internally for both Avionics bus bars.. but only one externally visible operatable switch
