This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is 1000 M ohm.
An oscillator whose frequency can be adjusted between 500 Hz and 5 kHz with the use of a...
This circuit protects the speakers in case the amplifiers have problems. With a continuous voltage...
This circuit is from the 80's and can be implemented with modern equivalent components. R1 is 2M5,...