sentences:  The coxswain typically wears a headband-mounted microphone, which is attached by a wire and quick release to the amplifier.Some units allow a walkie-talkie connection to the coach so they can use the amplification to speak directly to the crew as well.Rowing shells fitted with speed measuring impellers or GPS can report boat speed to the amplifier display, typically measured in Meters/second or 500 meters predicted split time.