I found this circuit in old book about electronics and this circuit related to PHILIPS company.
this circuit is used to magnificate the telehpone call when it put beside the telephone.
I want to ask about the transformer coupling i don't find it . how can i make it or replace by R coupling or RC coupling ?
i need help
the picture is attached
You can get mag pickups for telephones complete with suction cups. Putting it over the earpiece gives you the benefit of the phones internal anti-sidetone circuit.