Abstract: A tone generator circuit used in a frequency shift keying (FSK) channel in a frequency division multiplexing (FDM) system is disclosed. Each frequency shift between the mark and space tone frequencies is programmed to generate a sequence of discrete intermediate frequencies according to a sinusoidal modulation waveform to produce transmitted tone signals having minimum sideband energy and minimum distortion. A modulation clock generator produces a predetermined number of clock cycles per bit time of the baud rate of the channel. The modulation clock is used to produce a sequence of address signals used to address a PROM containing a set of multiplying code words. Each code word represents a different output tone frequency. The code words are used in a binary rate multipler to multiply a crystal controlled clock signal by the decimal equivalent of the binary code word. The multiplied digital frequency signal is also divided by fixed division factors to produce an output digital tone signal.

Abstract: A circuit for the systematic handling of conversation data from a calling party to a called party for use in a distributed processing telex exchange is disclosed. The customer terminations connected to the exchange are divided into a predetermined number of groups of terminations having a predetermined number of terminations in each group. Associated with each group of terminations is a frame memory which has memory capacity for storing a single bit of conversation data from every termination connected to the exchange. Associated with each frame memory is a vector memory which has a memory location associated with each termination in a group. Each vector memory location contains a frame memory address that addresses the location in frame memory containing the conversation data to be forwarded down to the termination associated with the current vector memory address.

Abstract: In a Telex switching system line terminator unit having means to transmit a character from the terminator to its terminal, in which the character is transmitted in a serial mode and terminated by a stop bit, an improvement in the manner of generating the stop bit is provided. A variable length stop bit is dynamically generated for each character transmitted such that the length of the stop bit is changed as the time required by the calling terminal to transmit the character to its terminator unit decreases over that required by the called terminator unit to transmit the character to the called terminal. Patterns in the rate of transfer of characters from the calling terminator unit to the called terminator unit are monitored to control the length of the stop bit.