Found in General Electric's 1969 documentation, this circuit uses two Foto Darlingtons to control the SCRs driving phases. SCRs can be equivalent current types.
This conventional astable multivibrator circuit with operational amplifier can be found elsewhere on...
The LDO series (Low Dropout) TPS80 from Texas Instruments (www.ti.com) can provide output voltages...
This circuit was found in a Hands On Electronics from the 80's. The circuit emits an audible alert...