Abstract: A terrestrial wireless telecommunication system is disclosed that uses an electronic scanning antenna to rotate a beam that carries communication messages between a base station and a plurality of wireless terminals. A base station transmitter transmits the communication messages to each wireless terminal, via the electronic scanning antenna, in a time-division multiplexed (“TDM”) data stream that is synchronized with the rotation of the beam, and a base station receiver receives the communication messages from each wireless terminal in a time-division multiple access (“TDMA”) data stream that is also synchronized with the rotation of the beam.

Abstract: A method and circuitry are disclosed which allow the operation of carbon microphones in telephone sets at low levels of average current. The microphone is connected to a pulse-generating circuit which energizes the microphone with pulses of current that effectively sample the incident acoustic signal at a superaudible rate. The level of each current pulse is chosen so that the microphone performs at the high signal-to-noise ratio associated with high current levels and the duty cycle is chosen to match the low average value of available current. The audio signal is recovered by demodulating the resulting PAM (voltage) output signals using a low pass filter. The level of the recovered audio signals is then amplified to the level required by the telephone transmission line. The sampling approach, using the carbon microphone as the sampling element, extends the utility of the carbon microphone to operation at low average current levels which hitherto were unusable because of low signal-to-noise ratio.