All measurements and data differs from way of measure, but a telephone shall work between 300 and 3400Hz.
This makes it difficult to hear if you say F or S....
The power from the carbon granulate transmitter equals an amplifier at about 1/1000 watt! (mean value)
The telephone impedance is typical 600 ohms, but may vary from less than 400 to about 900 in real life.
The induction coil acts as a transformer, and is made for matching the transmitter and receiver impedances. You may often have windings for reducing the sidetone.
Other data may be as this:
dsk