24 Volt DC is a very prevalent voltage used fashionable developed settings. This hobby circuit lower was designed to acknowledge four unlike 24v DC alarm input signals, which are followed by used to drive a single low power beeper. The beeper is a magnetic type with its own oscillator/driver. The four diodes form an “or else” gate so one solitary of the four inputs want cause the beeper to produce blast. A CMOS version of the widely held 555 timer is used to strobe the beeper on and rancid on something like 1Hz.