Phase Lock Loop

using ULN oscillator

4 -Transistor Tracking Transmitter

Circuit of rf impedance bridge

Hidden Transmitter Hunting

555 IC Oscillator

Cheap Low Power 3V 2Hz Oscillator

It could easily be modified to produce pulse frequencies from about one cycle per minute to a maximum of about 10KHz. It draws only about 1uA from a 3v battery.

Micropower CMOS oscillator, draws only 0.5ua

this circuit draws a mere 500nA from a 6v battery. It uses a very inexpensive C-MOS IC to produce a frequency of 2Hz. However, by changing the component values you can push it to 300Hz.

Low Distortion Crystal Oscillator