This interesting intercom circuit was obtained from an Argentine publication from the 1970s. Germanium transistors were used in the original and the transformers are of the type found in old transistor radios. We can change some resistors experimentally and taking advantage of the driver (T2) and output (T3) transformers of a radio, assemble the circuit with modern transistors. T1 will be an output transformer. TR1 and TR2 can be BC558 and the pair TR3, TR4 can be BD136. The speakers are 8-ohm.
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