Abstract: An emergency vehicle includes a siren signal generator emitting an electronic siren signal. A siren loudspeaker is coupled to the siren signal generator and emits an audible siren sound in response to receiving the electronic siren signal. The loudspeaker has two inputs. An impedance detector is coupled to the two inputs of the loudspeaker and measures impedance across the two inputs of the loudspeaker. The impedance detector outputs a loudspeaker presence signal if the measured impedance is within a predetermined range. A siren signal detector is coupled to the siren signal generator and emits a siren signal presence signal in response to verifying that the electronic siren signal has a set of predetermined siren signal characteristics. Logic circuitry emits an enable signal in response to receiving both the loudspeaker presence signal and the siren signal presence signal. A radio frequency transmitter transmits a radio frequency notification signal in response to receiving the enable signal.

Abstract: An emergency vehicle includes a siren signal generator emitting an electronic siren signal. A siren loudspeaker is coupled to the siren signal generator and emits an audible siren sound in response to receiving the electronic siren signal. The loudspeaker has two inputs. An impedance detector is coupled to the two inputs of the loudspeaker and measures impedance across the two inputs of the loudspeaker. The impedance detector outputs a loudspeaker presence signal if the measured impedance is within a predetermined range. A siren signal detector is coupled to the siren signal generator and emits a siren signal presence signal in response to verifying that the electronic siren signal has a set of predetermined siren signal characteristics. Logic circuitry emits an enable signal in response to receiving both the loudspeaker presence signal and the siren signal presence signal. A radio frequency transmitter transmits a radio frequency notification signal in response to receiving the enable signal.