Looking for a diagram of telephone line transformer circuit! Requirements: 1. 3.7V after transformer 2. 300mA or more current 3. AC rectified to DC 4. Indicate relevant parameters 5. Additional princi

Looking for a diagram of telephone line transformer circuit! Requirements: 1. 3.7V after transformer 2. 300mA or more current 3. AC rectified to DC 4. Indicate relevant parameters 5. Additional principle analysis... Telephone line transformer?

When standby, only about 30 volts DC at both ends of the line to maintain the standby state;

When the incoming call is ringing, the line is AC 75 volts at both ends, and it is not pure DC nor sinusoidal AC;

When the call state is in progress, there is only about 48 volts DC on the line to be modulated by the voice signal.