MODEM ULTRAFONICO CON DEMODULACION Y GENERACION NUMERICA DE SENALES DE ESTADOS LOGICOS, PARA SISTEMAS AUTOMATIZADOS DE TELEFONIA PUBLICA

摘要

An ultraphonic modem (modulator-demodulator) for automated public telephone systems is disclosed, which, for the purpose of reducing the absorbency of values compatible with the supply taken from the twin speech cable of the telephone line, comprises: a receiving logic circuit AE-DE which includes digital means of demodulating the logic states of a data carrier wave having correlated logic levels of ultraphonic but audible frequency; a transmitting logic circuit which includes means for the digital generation of logic states and the modulation of the said data carrier wave and passive analog means for separating the data carrier wave from speech frequency signals in reception and transmission (see Fig. 2).