unknown user wrote:
...
Thanks. I'll try that. My multimeter is a digital one, and can't make a
sound. It has 3 areas on the dial: voltage, current and resistance.
I guesss it must display some numbers on the display to indicate the
continuity.

I answered the mechanics but on reflection your above wording made
another response seem justified...

"Continuity" is determination of a path of possible flow through a
completed circuit. So, the measurement is one of measuring a
low-resistance path. When the switch is open, it creates a break in the
path so the resistance is essentially infinite. When closed, there's
essentially nothing but a short piece of wire between the base and the
other end so it's going to be a very low value--a few tenths of an ohm
will probably show up.

The continuity scale is provided for simply the purpose of finding
open/closed ciruits as a convenience since for the purpose the actual
resistance is not really of any interest--you're just interested in
whether the circuit is open or closed. Thus the sound indicator is
handy so you don't even have to see the scale.

HTH...