Very high quality Sonalert pulsating electronic alert type SBM616J operates on 6VDC upto 16VDC and produces a 78dB 2900Hz tone at the rate of 0.5 to 2 pulses per second (depending on voltage). Requires 3 to 12 mA of current and has 3 pins for power and mounting. Pin 1 is positive, pin 2 is no connection and pin 3 is negative. Size about 1.687" diameter x 0.62" thick (excluding pins). Brand new - Retails for $24 Each ($120.00 for 5). Sold as package of 5.