Abstract: A T1 digital carrier system having a transmitter, receiver and a plurality of intermediate repeater stages. Each remote repeater has a select switch for automatically selecting that the remote repeater be placed in loop-back mode should a combination of framing bits occur in the serial bit stream that matches that said remote repeaters address therein, thereby allowing remote testing of the communications link and repeaters. In addition, no additional test lines are required to verify a T1 communications link.

Abstract: A self-contained, pre-pay coin operated telephone wherein when the user removes a handset from a switchhook, a local dial tone is generated, prompting the user to enter a telephone number of a called party. Once the first digit of that telephone number has been entered, the locally generated dial tone is removed and the user completes the entry of the telephone number. Once the proper coin has been deposited, the internal computer causes the telephone to couple itself to a central office. The telephone number entered by the user is then sent to the central office under control of the internal computer. During this time, the microphone in the handset is muted such that the user cannot communicate through the telphone. Once the user hears the called party answering, then the user must actuate a push-to-talk switch to indicate to the computer that the party has answered.

Abstract: A self-contained, pre-pay coin operated telephone wherein when the user removes a handset from a switchhook, a local dial tone is generated, prompting the user to enter a telephone number of a called party. Once the first digit of that telephone number has been entered, the locally generated dial tone is removed and the user completes the entry of the telephone number. Once the proper coin has been deposited, the internal computer causes the telephone to couple itself to a central office. The telephone number entered by the user is then sent to the central office under control of the internal computer. During this time, the microphone in the handset is muted to disable communication. Once the user hears the called party answering, then the user must actuate a push-to-talk switch to indicate to the computer that the party has answered. The user is then allowed to speak to the called party and deposited coins are retained at the termination of the call.