Abstract: A method for multiplexing data between a set of line circuits and a set of time division multiplexed highway lines connected to a central switch. Line circuits are organized into clusters of fixed numbers of circuits. Groups of four clusters send data to and receive data from a single multiplexer/demultiplexer. One or more multiplexers may be connected to the same set of highways. A single master processor performs all of the highway and time slot assignments for the network. These assignments are made so that each cluster will transmit or receive during consecutive time slots on a single highway line. The multiplexer is capable of providing conductivity between any cluster and any of the highways. The highway and time slot assignments for each cluster may be altered by reprogramming the multiplexer.

Abstract: A signal level expansion system for use in a telephone device is described which includes a level expansion circuit and an optional microphone enclosure. The circuit includes a voltage divider circuit which is used as a variable attenuator. The voltage divider has a junction field effect transistor (JFET) in its takeoff leg. The signal provided by the voltage divider is applied to an amplifier and then fed to a switch which detects voice signals. When a voice signal is detected having a level above a predetermined threshold, a timing circuit is energized. The timing circuit is connected to the JFET and, when energized, tends to increase the resistance in the takeoff leg of the voltage divider, increasing the signal level applied to the amplifier. The microphone enclosure surrounds the sides of the microphone with layers of rigid and resilient materials.