Draw a schematic diagram of a simplex (one-way) battery-operated telephone communications system using a microphone in series with a battery at one end, connected to a pair of telephone wires whose other end is connected to a telephone receiver. Make the following assumptions: The microphone resistance varies from 5 to 500 ohms as the impinging sound pressure changes from its maximum to its minimum value; the telephone receiver at the distant end has a 160-ohm resistive impedance; the battery is 12 volts with negligible internal resistance; the telephone pair has a resistance of 4 ohms per 1000 feet.
a) How far could you talk with this system if you need to produce a 2.5-volt excursion at the receiver? What will be the magnitudes of the maximum and minimum voltages at the receiver?
c) Discuss the limitations on transmission #1. Express your answer in quantitative form (equations).