Microprocessor-based cordless telephone system

Abstract

A cordless telephone system is provided which includes a base unit operatively coupled to a user's telephone lines and a relatively compact portable cordless handset. Both the base unit and the cordless handset include a radio transmitter and a receiver which form a full duplex two-way FM radio link wherein the transmitter of the base unit and the receiver of the cordless handset operate on a first non-CB frequency and the transmitter of the cordless handset and the receiver of the base unit operate on a second different and distinct non-CB frequency. Both the cordless handset and the base unit include signal-injecting circuitry whereby a portion of the transmitter signal is injected into the input of the receiver to provide the local oscillator function for that receiver without undesirable cross-talk between the transmitted and received signals. The cordless handset also includes a keyboard for entering dialing information, security code identification switches for entering a user's identification code, a logic network responsive to the entered dialing information and security code information for generating data words indicative thereof, and an FSK-encoder including circuitry for generating a subcarrier frequency tone and circuitry responsive to the subcarrier tone for generating FSK-encoded equivalents of the data words. The FSK-encoded data words and the subcarrier frequency tone are superimposed on an FM modulated carrier for transmission to the receiver of the base unit. The base unit includes a microprocessor-based control system for controlling substantially all operational functions including ringing signal generation, security identification, line seizure, dialing signal generation, memory storage and recall, muting during identification and dialing, selecting T/R or R/O operation, and the like.