The MFOS Alien Screamer circuit consists of three main components: a voltage controlled oscillator, a low frequency oscillator and a one watt amplifier that drives a small speaker. The unit is powered by one nine volt battery and due to the low current drain of the LM324 it gets a lot of miles out of a nine volt battery. The circuit draws about 10mA. Battery B1 is switched into the circuit by S4 (SPST toggle switch). Capacitor C8 (470 uF) is the main supply filtering cap. It holds a good bit of charge which supplements the battery when the unit draws additional current. R22 and R23 (4.7K resistors) form a voltage divider that supplies a voltage level which is halfway between the battery's plus and minus terminals. This voltage is used as a ground reference in the circuitry. C9 and C11 (.1uF ceramic capacitors) are placed very close to the power pins of the LM324 to stabilize it's operation and filter power supply transisent noise from polluting the op amp's bias network
