6AC7 Amplifier (T450E)

Obtained in MIT documentation, this 4-stage circuit has high gain for small signals. The power supply sources 150 V.

Sound Activated Relay (CB5989E)
This circuit makes use of a low impedance microphone. The relay is according to the supply voltage...
Low Power Astable Multivibrator (MSB037E)
The astable multivibrator shown by figura 1 has a very low current drain and can be powered from 6...
Output stage with the AC117 (CB4278E)
This step is also suitable for the AC188k and SK3004 transistors and was found in a 1980s...