Ah right it's the keypad only ones you need to be careful of.
I assume that the bell has been wired normally, so at the panel, find the whole cable going to the bell, and you will (should) have a +ve and -ve hold-off wire, going to the normal 12V supply, a wire going to a terminal marked 'BELL' or similar, possibly one going to 'STROBE' and crucially, one going to a terminal marked 'TR', 'TA' or 'TAMPER RETURN'. If you remove this wire, connect it to the -ve lead of your multimeter and the +ve multimeter to any 12v feed - if it reads 12V, the tamper on the bell is closed. If you're reading nothing, the tamper is probably open.
Or at least, that's the theory, of course I don't know much about your installation, bell setup, etc... but that would be normal.