Two tone alarm with LM3900

This be Two tone alarm use op-amp IC number LM3900 (Quad Amplifiers) perform produce the frequency square wave 2 level , be high frequency and low then mix the sound in the end danger beep that is appropriate it has can to link up a loudspeaker with ,using power mosfet then have better use transistor which complicated and not durable. This circuit convenients for power supply 9V to 12V sizes and 8 ohm 20watt size loudspeakers will by large-sized have a voice loud small-sized better.

Two tone alarm circuit using  LM3900