This audio oscillator is from a 1957 Raytheon publication. The tone generated depends on C2 and C2 and the handset must be high-impedance magnetic. Equivalent transistors can be tested.
The integrated circuits in this application are not very common today. One consists of an A / D...
Found in the Encyclopedia of Electronic Circuits Volume 5 of 1995 this circuit has the gain...
The output power of this amplifier depends on the supply voltage that can be between 3 and 16 V....