Telephone receiving terminal for telecopier - provides identification signal after establishing contact comprising synchronisation and additional BCD numbers

摘要

The receiving terminal is for automatic communication over a telephone line. After establishing the telephone connection the terminal transmits an identification message comprising tones repeated several times. The message is digitally coded in binary and comprises a bit synchronisation part, a message synchronisation part and several binary coded numbers. The bit synchronisation comprises alternate 1's and 0's, while the message sync. comprises a series of 1's and 0's ending with 0. Each number comprises four groups of bits in BCD and a parity bit. 1 and 0 are transmitted on two frequencies such as 500 and 2500 Hz.