Transmission system for characters on telephone keyboard - uses multiple frequency code signal from terminal including transmitter, receiver and visual display panel

摘要

The character transmission system by telephone involves a keyboard unit with, typically, 48 keys arranged on a panel in a matrix arrangement, the keys representing alphanumeric data and special characters. The internal circuitry includes a transmission circuit. with a transcoder with a decimal code, a register, a number representing the code extension and a code detector. At the other end of the transmission line is a similar keyboard unit with a reception circuit activated by the multiple frequency signals receives. The system can transmit written message by telephone between similar terminals. The alphanumeric data may also be used for coded data in ASCIL or for writing computer programmes in COBOL, FORTRAN etc. Standard telephone equipment can be used in conjunction with a simple keyboard. The extension to the code to multiple frequencies enables a single code unit to represent one of four characters.