Amplifier with different output (CB9057E)

This circuit was found in a 70s National Semiconductor manual. It has a different output way for coupling to the speaker.

Adjustable reference (CB21540E)
We found this circuit with 5.3V zener in a Philips publication from the 60s. The op amp could be a...
Phase separator (CB8104E)
This circuit provides signals in phase with the input and with the phase inverted. The circuit was...
Simple liquid level sensor (CB20729E)
This sensor with two transistors triggers a relay according to the supply voltage. The power...