Abstract: In a voiceband data multipoint network, each tributary modem transmits, in a trailer which follows the user data, a tributary modem identification, a sequence number which advances for each start-up and a checksum. The observation at the receiver of a gap in the series of sequence numbers in messages determined to have originated from a particular tributary modem is used to accurately compute a missed message rate for that modem.

Abstract: Modems, data service units, application modules and other data communication devices, installed in a common equipment cabinet, are interconnected by way of a time division multiplexed bus. Time slots assigned to the various devices recur at a number of rigidly-spaced access periods across each time division multiplex frame. The rate at which the access periods occur and the total number of access periods that make up each frame are chosen in such a way as to accomodate a mix of devices having respective bus access rates wherein there is at least one pair of rates for which neither rate of the pair is a multiple of the other. The process of allocating access periods to the time slots is carried out using a known lemma to identify linear Diophantine equation solutions.

Abstract: A security file system for a portable data carrier provides improved security for the data carrier and for data contained in files in the data carrier. Although the data carrier may be embodied to look and feel much like an ordinary credit card, it contains a computer and a programmable memory with operating power and input and output data provided through a contactless interface. In order to provide security for the data carrier, the security file system on the data carrier includes a stored access code for verifying the identity of an individual attempting to access the data carrier, and an appropriate routine for limiting the number of unsuccessful attempts to access the data carrier. The security file system is also configurable to include select ones of multiple stored access codes for enabling the retrieval and modification of data in corresponding select ones of the files. The routine similarly limits the number of unsuccessful attempts to access these files.

Abstract: An improved Manchester code receiver is disclosed which samples the received signal and subtracts from that sample a previous sample of the received signal delayed by a half-bit time interval. A timing extractor selects sample timing from the central zero crossing of the received signal. The sample time is selected to be a quarter-bit time after the zero crossing time of the received signal.

Abstract: A probe for providing noise measurements of an electrical circuit includes at least one loop of wire connected to a plurality of conductors. The loop interconnects one or more signal-carrying ones of the conductors to one or more of the conductors carrying ground and has a portion which is substantially straight or is deformable to follow the path of a conductor in the electrical circuit. Preferably, the loop is formed so that this straight portion terminates in a right angle bend at each end. This loop serves as an inductive pickup which avoids the need for contact of the probe to the circuit under test and, thereby, provides more accurate noise measurements.

Abstract: A PBX system is responsive to an incoming call which is directed to an adjunct of the system for sending a ringing signal over a station facility to the adjunct. When the adjunct goes off-hook, the system outputs to the adjunct over the station facility multi-frequency tones containing information associated with the incoming call prior to establishing a connection between the adjunct and calling party. The information selects the proper operating mode of the adjunct and provides other call processing information to the adjunct. The adjunct communicates information to the PBX using a switch-hook flash and multi-frequency tones.

Abstract: When the disclosed frequency-hopping communication system is initially enabled, it detects another system operating within range by listening for a predefined radio frequency of a fixed duration. When that particular frequency is detected, the system knows that a master system is operating within range and is utilizing a first predetermined group of communication frequencies and, consequently, selects a second, third, etc. predetermined group of communication frequencies. If the particular radio frequency is not detected, the system becomes the master system, selects the first predetermined group of communication frequencies for intra-system communication and begins transmitting the predefined radio frequency to indicate its master status.

Abstract: Currently, metallic loops are tested for shorts, opens and grounds by applying a test signal (DC or 20 Hz) directly to the metallic looop. A test signal cannot be applied to any part of the network other than the metallic loop because it will be blocked by the A-to-D converters and the hybrid of the system before it can reach the metallic loop.In this invention, digital signal processing is used to test a metallic loop for shorts, opens, grounds and the presence of loading coils from a remote location. Direct metallic connection to the metallic loop is no longer necessary.Briefly, a test signal, in digital form, is fed into the network at some convenient location remote from the metallic loop that is to be tested. As the signal passes through the A-to-D converter from the digital section of the network to the analog metallic loop, it is converted by the A-to-D converter into an analog signal having a specific frequency and a predetermined amplitude.

Abstract: A repertory telephone dialer includes a memory for storing two telephone numbers and one telephone call payment number. Activation of a switch on the dialer causes the first telephone number to be dialed; thereafter, the dialer responds to a Calling Card Service-Prompt Tone by transmitting the call payment number. The call payment number corresponds to a credit card number of the party to be billed for the call. The dialer is constructed as an adjunct device that connects to an existing telephone set by merely rearranging cords. Included on the front surface of the dialer is a recessed area that accommodates a photograph or graphic rendering of the party whose telephone number is dialed and who typically makes payment for the call. Activation of another switch on the dialer inhibits the remote billing feature by causing the second telephone number to be dialed.

Abstract: In a voiceband data multipoint network, each tributary modem transmits, in a trailer which follows the user data, a tributary modem identification, a sequence number which advances for each start-up and a checksum. The observation at the receiver of a gap in the series of sequence numbers in messages determined to have originated from a particular tributary modem is used to accurately compute a missed message rate for that modem.

Abstract: An easily assembled connecting block provides interconnection between modular plugs and insulated telephone wires or the like. The connecting block includes: (i) a metallic lead frame comprising a number of flat elongated conductive elements that terminate in closely spaced flat wires at one end thereof, each conductive element terminating in two pairs of insulation-displacing contact fingers at the other end; and (ii) a dielectric block for receiving the closely spaced wires within a jack housing contained therein and for supporting the metallic lead frame. In one embodiment the connectors are an integral part of the lead frame itself and are "sandwiched" between a pair of dielectric blocks, each block having a plurality of corresponding slots for guiding wires into the region between opposing contact fingers of the connectors.

Abstract: The process of interpolating between two different sampling rates at any point in a sampling interval is obtained using a transversal filter arranged as a continuously variable digital delay line in which the tap coefficients of the delay line are made to be a function of the coefficients of an nth degree polynomial and the delay between the two sampling rates.

Abstract: In a user-interactive display-based telephone system, the present invention permits an automatic display of a repertoire of telephone command items most likely to be utilized by a user, thus providing one-touch access to such item without requiring either explicit programming of a command repertoire or a search by the user through the history of previous commands. This is accomplished through the use of three heuristics which consider frequency of command use, recency of command use, and previously failed commands. These heuristics may be implemented either separately or together in the system.

Abstract: A card guide for guiding a circuit card towards a connector mounted on a backplane of electronic apparatus includes a first member which is mounted on the backplane and a second member releasably joined to the first member, the second member having a slot for accommodating an edge of the card for aligning and guiding it towards the connector.

Abstract: The cordless static electric discharge unit for discharging static electricity from a human body into the air. The apparatus consists of a discharge unit attached to the wearer's wrist by a wrist strap. The discharge unit utilizes a radioactive source to ionize air and the flow of the ions discharges the human body. If the human body is at a positive potential with respect to ground, the negative ions flow to the human body whereas the positive ions flow from the discharge unit to a grounding point. The discharge unit is mechanically constructed such that sub-atomic particles emitted by the radioactive material are prevented from entering the human body or flowing into the surrounding air.

Abstract: A key switch utilizing a buckling compression spring to move a switch actuator mechanism includes a cylindrical core of resilient material located within an opening formed by the coils of the compression spring to attenuate the acoustical energy generated by the buckling and unbuckling action of the spring.

Abstract: In a processing system (FIG. 1), peripheral boards (101-103) interconnected by a stack bus with a system board (100) each have an optical emitter (163) mounted on one face and an optical detector (162) mounted on the other face. The system board has an optical emitter mounted thereon. Emitters and detectors are arranged in a daisy-chain fashion: the emitter of one board faces the detector of the next board. To assign I.D.s (e.g. addresses) to boards, the system board turns on its emitter and transmits on the bus an I.D. The adjacent board's detector is illuminated and causes the board to latch the I.D. The system board turns off its emitter, signals the adjacent board to turn on its emitter, and transmits another I.D. on the bus. The next board's detector is thus illuminated and causes the board to latch the I.D. The system board performs the procedure for each peripheral board.