Abstract: There is provided a scheme for centering data prior to detection. It comprises: determining carrier frequency error, and pre-adjusting the data detection process to compensate for that error throughout the ensuing data detection. This scheme for reliable multi-level data detection further comprises: upon detection of carrier presence, determining carrier frequency error, gating a voltage associated with the frequency error to the differential amplification process to establish common mode rejection and compensating for that error throughout the ensuing multi-level data detection, and then analog-to-digital conversion of the differentially amplified multi-level data. A scheme for computationally centering the subsequent data detected to compensate for the error is also provided.

Abstract: A telephone system employs a novel message system for calling parties. The switch controller includes selectable and programmable announcement machines, while the telephone devices include indicators which allow call transferees the ability to determine the reason the call was transferred, e.g., the called telephone was busy, did not answer or the called telephone party is in conference. When desired, a telephone party is capable of programming the switch controller to reply to any particular incoming phone calls with one of a number of customized or preselected messages.

Abstract: A simulcast transmission system is provided where a reference signal transmitted from a central station is utilized to phase-lock transmitters located at remote stations. The remote stations include a receiver for receiving the transmitted reference signal and a signal conditioner for conditioning the received reference signal for application to the transmitters. The transmitters include a phase-locked loop which may be followed by a multiplier for providing transmitter signals of predetermined frequencies. All the transmitters at the remote stations are phase locked to the reference signal transmitted from the central station. In the event that the reference signal transmitted by the central station is interrupted, the signal conditioner of the remote stations will operate in an open-loop fashion to provide the conditioned reference signal during the interruption.

Abstract: The operational status of equipment located at a base station is reported to a remote control terminal. The same audio channel that is used for sending audio signals and control signals to the base station is also used to carry the report signal. The control signals to the base station and the report signals from the base station are encoded tone burst signals. The report signal provides an indication of the proper receipt and execution of a control signal by the base station equipment. Equipment diagnostic signal and periodic checks of equipment performance are also reported by this system.

Abstract: A control console including a transceiver, a plurality of terminal stations positioned at spaced apart locations remote from the console and each including a transceiver connected to the console by RF or a wire line, and a plurality of call boxes positioned at spaced apart locations adjacent to each terminal station and including a transceiver in communication with the terminal station. When the hand set of a call box is lifted from the cradle a tone is transmitted through the adjacent terminal station to the console which then keys on all terminal station transmitters to indicate a busy line at other call boxes and to provide a ringing signal at the call box being used. Subsequent to transmission of the tone, a signal indicative of the address of the box and the condition of predetermined portions of the box is automatically transmitted to the console. When the console operator answers, full duplex communication is provided between the call box and the console.