If already connected to the side RAC connector, the existing Standard or Advanced RSM can be used when the STP is attached to the car kit.
Alternately, a speaker microphone can be attached to the car kit. The speaker microphone has a separate emergency button (soft key). The unit is supplied with a hook switch bracket.
The speaker microphone appears almost identical to the fist microphone but includes a 0.5 watt loudspeaker.