Abstract: The subject arrangement provides a last number dialed automatic redialing capability for each line of a multi-line telephone station set or attendant console. This is accomplished by maintaining a centralized last number dialed table on a per-line basis in the telephone switching system processor. When a subscriber subsequently accesses a line and operates the REDIAL key on the station set, the system processor retrieves the stored last number dialed for that line and completes a call connection to the identified destination.

Abstract: In private PBX communication systems the number of dialing digits required to establish a connection between stations at different PBXs of the system includes PBX location code digits and station address digits. Abbreviated dialing is accomplished by using one or more digits of the PBX location code as both location code digits as well as part of the digits which comprise the station address.

Abstract: A data communication method and circuitry which uses a compatible subset of a standard high level data link control (HDLC) protocol to control link level communication between a digital terminal and a switch. The use of the subset of HDLC protocol reduces the complexity of the digital terminal design while maintaining communication compatibility with a switch which uses either the standard HDLC protocol or the subset of HDLC protocol.

Abstract: Half-duplex switched carrier operation is emulated in a full-duplex voiceband data transmission system by utilizing predetermined signal indications in each channel to signal the initiation and termination of user data in that channel and thus to control the Receive Line Signal lead extending to the terminals at respective ends of the transmission channel. The signal indication which signals the initiation of transmission is illustratively two scrambled spaces inserted into an idle-state sequence of continuous scrambled marks. The signal indication which signals the termination of transmission is illustratively a stream of 65 unscrambled marks.

Abstract: A method and apparatus for rapid initialization of the transversal filter efficients in an echo canceler or echo measurement device is described. During initialization, a first data sequence is applied to a transmission channel, and an error signal representing the difference between the resulting echo and a replica thereof generated by the transversal filter is formed. The coefficients used to form the replica (in the case of an echo canceler) or to model the transmission channel (in the case of an echo measurement device) are then updated as a function of the error and a second data sequence which is orthogonal to the first sequence.

Abstract: Contention among a plurality of synchronous and asynchronous devices connected to a shared communication medium for access to time slots in a sequence of frames is resolved by assigning a unique priority word including a priority code prefix to each device and granting access to a given slot by comparing the values of the priority words assigned to competing devices. The priority code prefix is assigned as a joint function of whether synchronous or asynchronous communication is desired and whether synchronous communication is being initiated or continued. In each assignment protocol, synchronous communication is enabled by assuring any device that initially gains access to a particular time slot continued access to the same slot in succeeding frames. If desired, devices with synchronous access may relinquish unused time slots to asynchronous traffic, while reserving the ability to resume synchronous communication.

Abstract: A transient power alarm is often the result of a traffic overload placed on a communication system circuit carrier circuit. The disclosed power control arrangement recognizes such transient power alarms and outputs a special message to alert the system user to the possibility that traffic grading across carrier is unbalanced. The control arrangement also monitors the time that the system is powered solely by reserve battery and sheds its traffic load if the time that the system is operating solely on reserve battery exceeds a first threshold. Also, the system is programmed to automatically disable itself if the reserve battery time exceeds a second threshold.

Abstract: Apparatus and method are disclosed for checking the time slot data word integrity of data communications in a time multiplexed communication system. A predetermined control bit of each data word of a data frame is alternately switched from its normal control bit function to a bit of a pseudo random sequence (PRS) for time slot data word integrity checking. During alternate data frames a checking circuit compares the predetermined bit of received consecutive data words against consecutive bits of a reference PRS and outputs a time slot cross connect error signal when a difference occurs.

Abstract: The subject device control system provides a new method of determining when resource consuming loads are to be disabled to prevent the total resource consumption from exceeding a predetermined threshold. This system bases the decision making process on a customer controllable risk parameter, past consumption, past load shedding activity and predicted future load activity. The controlling algorithm is applied to the present resource consuming situation for a plurality of different time interval configurations and the worst case result of these computations is used to control the load shedding.

Abstract: An automatic message waiting alerting arrangement in a telephone switching system. Messages for parties served by the system are automatically and manually generated and stored in a database. A message waiting indicator associated with a station is automatically activated only when the database contains an unaccessed message for the station, even though other accessed messages may be retained in the database for the convenience of the station owner. An "accessed" indicator included with each stored message is set to an "unaccessed" state when the message is initially stored. The indicator is set to an "accessed" state when the corresponding message is accessed by an authorized party. At the termination of an access session, the data base is searched for unaccessed messages for the station and the message waiting indicator is activated only if at least one unaccessed message for the station is found.

Abstract: A digital processor based voiceband modem that provides computers and terminals access to telephone lines and performs line control functions to originate, answer and terminate data calls in addition to converting baseband signals to voiceband and voiceband signals to baseband. The modem utilizes a signal processor that executes various signal converting algorithms under control of selected sets of instructions and further utilizes a digital processor that executes line control algorithms for alternative modes (i.e., originate or answer) of the data modem. An outgoing or incoming call enables the appropriate mode and, during the execution of the corresponding line control algorithm, various sets of instructions are selected to execute signal converting algorithms appropriate for the enabled mode of a specific one of various data modem types.

Abstract: There is disclosed a business communication terminal structure having a modular switchhook and cradle assembly which can be easily located on either side of the terminal housing to receive a telephone handset. The unused housing side surface aperture is covered using a blank tight fitting cover plate which blends with the terminal housing.

Abstract: Disclosed is a charge redistribution codec employing a two capacitor network for developing a progression of reference voltages having a binary relationship to each other for each analog input sample to be encoded. Linear encoding of input samples is achieved with the use of two such charge redistribution networks, with one developing positive reference voltages and the other developing negative reference voltages. Analog input samples are placed in an encoding capacitor and based on the polarity of the voltage across the capacitor either a positive or a negative charge is added iteratively to the capacitor in the direction of driving the voltage across that capacitor to zero. A code is developed by assigning at each iteration one value to an output code bit when a positive voltage is added and the opposite value to the bit when a negative voltage is added.

Abstract: The telephone mounting apparatus comprises a rectangular frame base unit having a protrusion at one end and two slots at a second end for accepting either of two brackets. A telephone desk stand is constructed by inserting a first bracket into the slots in the base unit. The desk stand utilizes a first load bearing surface of the protrusion. A telephone wall mounting is constructed by inserting a second bracket into the slots in the base unit. The wall mounting utilizes a second load bearing surface of the protrusion.