Abstract: A telephone instrument creates spatially simulated sound signals from signals received from a telephone line. The monaural signals are separated to two left and right channels. In each channel, the signals are processed via a direct path, an early reflection path including a finite impulse response filter and a reverberant decay path including all-pass filter. In each channel, the outputs from the three paths are summed with different weights.

Abstract: A telephone caller is permitted to retrieve his call from the central voice services feature of an unavailable called party, and resume the call progress by substituting a calling feature of his own. In a telephone system including a telephone switching facility and a voice features server, provision is made for enabling a calling party to invoke an appropriate calling party feature such as a ring back feature or an override feature, and thereby subsequently achieve a real time conversation with the called party instead of simply being able to leave a voice message for the called party.

Abstract: A key telephone system (KTS) or a telephone private branch exchange (PBX) card is integrated into a personal computer to provide telephone system features. The telephone card includes a call controller, a switching network and an interface bus controller for coupling data signals between the PCI bus and an internal bus of the call controller whereby the telephone card is able to communicate with resources of the PC such as a LAN and a hard disk bulk memory for executing telecommunications functions. In this arrangement the PCI bus must carry both asynchronous data processing and control signals as well as reformatted synchronous signals. The addition of a synchronous bus for transporting synchronous signals is used to couple these signals between the switching network, a telephony features controller and the hard disk bulk memory. The use of the synchronous bus provides for improved telephone traffic capacity and PC functionality.

Abstract: The eligibility of all bidirectional links interconnecting a plurality of nodes in a network is determined based on the free bandwidths in both directions of the links and the bandwidth required for transmitting messages between a source node and a destination node in the network. The determination is exercised as to both ends of a link. Then, the link is determined whether or not it is eligible to become part of the shortest route. The determined eligibility of the links may provide a rapid shortest route selection, which will be executed later, because the route selection steps are not executed for ineligible links.

Abstract: An analog switch matrix provides limited connectability between a plurality of n telephone line appearances and a lesser plurality of m line interface circuits each connected with a communication path in a telephone system. The analog switch matrix includes n groups of 3 crosspoints each being operable to connect and disconnect a one of the n telephone line appearances at any of 3 line interface circuits, each of which is connectable to more than three of the line appearances. A switch matrix controller directs switching operations of the analog switch matrix in response to transitions to OFF HOOK states having been sensed at line appearances and in concert with the call controller in the telephone switching system. In a telephone system with a concentration ratio of 4:1 the grade of service is maintained by performance of a call transfer between ones of line interface circuits at any time during a call progress.

Abstract: An intrusion detection electronic circuit package, includes a containment wall in combination with first and second transmission lines being organized in patterns spaced adjacent one another. Electronic circuitry, residing within the containment wall, includes a transmitter for transmitting signals in anti-phase relationship via the first and second transmission lines respectively. A receiver receives signals from the transmission lines and a detector connected to the receiver uses EXCLUSIVE OR logic to detect any significant in-phase components or interruptions in the signals received at the first and second inputs of the receiver. Disturbance of either transmission line in any attempt to breach the containment wall is likely to be detected.

Abstract: A telephone instrument creates spatially simulated sound signals from signals received from a telephone line. The received signals are directed to left and right channels. In each channel, the signals are processed via a direct path, an early reflection path including a finite impulse response filter and a reverberant decay path including all-pass filter. In each channel, the outputs from the three paths are summed with different weights.

Abstract: A post assembly process for enabling a manufacturer of acoustical communications apparatus, such as telephones and the like, to conveniently trim a sensitivity characteristic of an electret microphone therein, after assembly of the apparatus, whereby a uniform performance standard may be adhered to. When the acoustical sensitivity characteristic of the electret transducer is measured to be greater than a predetermined value, the transducer is exposed to X-ray radiation until the measured sensitivity characteristic has been reduced to the predetermined value.

Abstract: A line interface circuit supplies energizing direct current from a power source via tip and ring leads of a two wire communications line connected with a telephone apparatus, and also couples alternating current signals between the telephone line and an associated telephone facility. The line interface circuit is provided with tip and ring terminals for connection to the tip and ring leads, and power terminals for connection to the power source. Coupling circuitry is connected in series with the tip and ring terminals for providing paths for the energizing direct current and for the alternating current signals. An active tip feed circuit is connected in series between the tip terminal and the coupling circuitry for providing a tip feed path having a predetermined resistance while the telephone apparatus is in an OFF HOOK state and having a much higher resistance in response to an excess of voltage at the tip terminal.

Abstract: In a hands free communications terminal apparatus, a loudspeaker and a microphone are permitted to be simultaneously active. A controller monitors signals in transmit and receive paths to direct operations of transversal filters to provide two echo canceller functions, one for the microphone and one for a telephone line so that most unwanted echo and feedback is removed, to prevent the howling and squealing sounds that commonly occur when the loudspeaker and the microphone are both active. Remaining echoes are removed by voice switching of loss between transmit and receive paths, wherein the amount of loss is determined in response to characteristics of the telephone line and the operating environment of the terminal apparatus.

Abstract: Integrated Services Digital Network (ISDN) terminal equipments (TEs) are remotely powered from a central source via line interface circuits. One function of the line interface circuit is that of conducting energizing direct current for the associated telecommunications terminal equipment while providing effective overcurrent protection in spite of widely variable load current requirements which occasionally may mimic a faulty over current condition.

Abstract: A key telephone system, having ports for connection to telephone lines of a telephone exchange and ports for connection of terminal apparatus including key telephone sets, is provided with the ability to distinguish if an intended call or feature access involves more than the key telephone system. If so, a signalling protocol of the telephone exchange is emulated on behalf of the terminal apparatus and transmitted via one of the telephone lines whereby the progress of the call or feature access continues, as if a user of the terminal apparatus had initiated the signalling protocol of the telephone exchange.

Abstract: An equipment shelf, for removably retaining circuit boards at selectably spaced locations in a system, includes side panels being connected in a spaced relationship one with another by extruded aluminum cross connecting members. A board slider retaining element in the form of an elongated polycarbonate strip is laterally and removably disposed in each cross connecting member. Each strip defines fastening locations, mounting orifices, being arranged in a predetermined pattern. Each of a plurality of board sliders is longitudinally fixed between a pair of the fastening locations, so that lateral spacings of circuit board positions in the equipment shelf are defined by the fastening locations. Lateral spacings of circuit board locations for a system are conveniently selectable by manufacture or choice of polycarbonate strips with an appropriate arrangement of the mounting orifices.

Abstract: An equipment shelf includes circuit board slides being arranged to support edges of circuit boards, whereby the circuit boards are removably retained in a system. First and second end panels are fixed in a spaced apart relationship by a pair of front cross connecting members and by a pair of rear cross connecting members. Each of the circuit board slides is carried between an inner edge of a front cross connecting member and an inner side of a rear cross connecting member. As each board slide is overlapped by only one of the cross connecting members, the cross connecting members are more widely spaced from front to back than would otherwise be the case, whereby greater area for a flow of a ventilating medium is available.

Abstract: An electronic system includes at least one element which is operative in response to clock signal pulses, of less than a maximum frequency of occurrence, from a clock signal source. A dither means is connected to the clock signal source for causing the frequency of occurrence to be varied such that electromagnetic radiation which accompanies the normal operation of the system is of a lesser interference effect than if the frequency of occurrence were substantially monotonous.

Abstract: An interface circuit provides for coupling of communications signals between a conductor of a transmission path, and a key telephone system and provides for protection against electrical energies, as may be associated with transient electrical event occurrences along the transmission path. The interface circuit provides for coupling of some of these transient electrical energies from the transmission path conductor to an earth ground. The interface circuit includes a plurality of electrical components and a plurality of electrical conductors being fixed to either of first and second surfaces of a sheet of electrically insulating material. The electrical conductors are spaced apart from each other by at least a predetermined amount. Some of the electrical conductors connect the electrical components of the interface circuit in a workable arrangement whereby the communications signals may be coupled.

Abstract: A telephone line interface circuit includes a transformer with tip and ring windings connected between tip and ring feed resistors and tip and ring leads of a telephone line for feeding energizing current from telephone facility to the telephone line. A secondary winding in combination with the tip and ring windings couples a.c. signals between the facility. A capacitance is connected in combination with the secondary winding to simulate a function of a capacitance as would normally be connected between the tip and ring windings in prior art circuits, but without the problem of feed resistor interference at lower voice band frequencies. Network and component values are inserted between the secondary winding and an electronic hybrid circuit whereby the line circuit is precisely tailored for anyone of several national telephone line standards.

Abstract: A telephone line circuit transformer couples tip and ring leads of a telephone line to a telephone facility. Tip and ring transformer windings are connected in series with the respective tip and ring leads, tip and rings feed resistors and terminals of a battery power source for supplying energizing current to the telephone line. A capacitor is connected between a junction of the tip winding and the tip feed resistor and a junction of the ring winding and the ring feed resistor. A compensating circuit is connected to drive a compensating winding in current opposing relationship with respect to differential alternating current signals in the tip and ring windings and being within a range of voice frequencies within which an impedance of the capacitor is significantly shunted by the feed resistors.

Abstract: A line interface circuit supplies energizing current for operation of a two wire communication line and couples a.c. signals between the communication line and a telephone facility. Tip and ring rails are resistively connected to the communication line by matched feed resistors in a resistance network also including tip and ring taps. Active impedance circuits in an a.c. signal coupling circuit terminate the tip and ring rails with a predetermined impedance, via the feed resistors, in response to voltages at the tip and ring taps. Active resistance valving circuits in a direct current feed circuit supply the communication line with energizing direct current via the tip and ring rails and feed resistors. The valving circuits may be controlled to limit current for shorter lines and the functions of the a.c. signals coupling circuit may be optimally altered in response thereto.