Is there a PA or loudspeaker of some sort?  Or do
your coworkers listen to a stereo at adolescent
volumes while working?

Have you considered a suction cup microphone of
the sort that is usually used to listen in on phone
conversations?  Stick it to the ringer speaker on
the cell, hook it through the PA, and there you
go.

If you REALLY want to make some gizmo to do
it, a VOX-type circuit wouldn't be inappropriate.
That way, loud environmental noises wouldn't
set it off, as the ringer would always be louder.

For myself, I just turn on vibrate, put it in the
holster, and tuck it INSIDE my belt and pants
against my hipbone.  VERY hard to miss.

Mike H.

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