FAX-telephone interface circuit

摘要

An improved telephone interface box which interfaces an incoming telephone line to either a modem or a telephone handset is disclosed. The choice of connection is made by a controller that answers incoming calls and determines if the call is to be directed to the modem or the telephone line. The controller determines the destination of the incoming call by detecting tones on the telephone line or by examining the response of the caller to a voice prompt. If the controller determines that the incoming call is to be directed to the telephone handset, the controller generates a ring signal having substantially the same cadence as that detected on the incoming line and sends that ring signal to the telephone handset. If the handset goes off-hook during the time the controller is making its determination as to the correct destination for the incoming call, the controller suspends its operation until the handset is placed on-hook or a predetermined time interval elapses. The controller also allows the handset to assert priority over an existing connection by rapidly depressing the off-hook switch on the handset.