Check the listing for details. Audio Trigger Circuit Speaker Input = Control Volts Output Level Sensing Switch. Condition: New. Listed at 25.00 USD. N-902 AUDIO AUTO-TRIGGER CIRCUIT The N-902 Audio Auto Trigger Circuit was designed to sense the presence of a low level audio signal feeding a loudspeaker or headphones. When a signal is detected, the N-902 produces an output Voltage that can activate a relay or turn on a component. This output will stay on for around 15 seconds after the input signal is dropped. Great for home, portable, pro, and car audio systems. Yes, the N-902 will produce a Control Voltage from the headphone output of an iPhone, Smart Phone, iPad, etc. The output of the N-902 supplies +12 Volts DC (actually anything from +9 Volts up to +20 Volts DC works just fine) to activate aftermarket automotive audio components, or home audio relay. If your vehicle has a factory type OEM deck / source unit that does not have an electric antenna control lead or other turn-on/off control Voltages, the N-902 can be connected across any speaker in the system to activate relays, components, lights, etc. The N-902 works by sensing 100mV or so of speaker Voltage from the terminals of any active speaker or speaker leads. When the speaker Voltage is present, the circuitry activates and +12 Volts DC is produced on the GREEN wire. Wiring Instructions: Connect the RED wire to +12 Volts DC Accessory (Fuse at 2 Amps.) A 120 Volt AC to 12 Volt DC "wall wart" power supply works fine. Connect the BLACK wire to the Chassis Ground (Negative Supply). Connect the Paired CLEAR wires to the + and – terminals of any active speaker. (Polarity is not important.) The GREEN wire is the +12 Volt DC Output and should be connected to the Turn-On/Off lead of your aftermarket amplifier, equalizer, etc. The Blue LED indicator on the top of the plastic enclosure will illuminate when the N-902 is triggered. Notice that there is a delay to account for lapses in spoken word and musical passages. The N-902 measures 2" x 1.5" x 1".