Intercom with telephone (CB7829E)

Old phones with dials can be used in a simple home intercom system, as this circuit from Popular Electronics from the 90's shows.

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Square Oscillator (CB23733E)
The circuit shown in figure 5 generates square signals based on a transconductance operational amplifier...
Power supply circuit (CB25185E)
By adding a transistor to the output and some polarization features we can obtain a higher output...
High Voltage Pulse Generator (CB26143E)
Found in the 1990 special issue of Radio Electronics Experimenter magazine, this circuit uses an...