The ADC801 is not an easy component to obtain today, but the configuration is worth reference. The circuit is from National Semiconductor's Linear Applications Handbook.
This oscillator is enabled when a high level is applied to the control input. The operating...
This circuit uses two oscillators to produce a sound that seems the sound of a ring-bell. The...
Found in a Popular Electronics from the 9s, this circuit has output for RS-232 interfaces and current...