Abstract: A loss of optical input detector is disclosed disposed to receive a signal voltage from a fiber-optic receiver indicating that the optical input has dropped below a preset threshold. The detector includes a voltage follower connected to the fiber-optic receiver which passes to the detector circuit the signal voltage. A comparator circuit receives the signal voltage and compares it to a reference voltage. When the signal voltage is greater than the reference voltage the comparator produces and applies to an alarm circuit a positive voltage signal. This positive voltage signal turns on the alarm circuit. The alarm circuit provides a visual alarm indication and a logic signal to a controller interface indicating a loss of the optical input signal.

Abstract: An Integrated Services Digital Network module includes a time division multiplexed switching network. Subscribers are connected to the time division multiplex network via a number of facility interface cards. These facility interface cards provide for two wire subscriber connection, four wire subscriber connection, T1 line connection and for three port conferencing arrangements. Originating and terminating multiplexers connect the facility interface cards to the time switching network. Another subsystem provides protocol interfaces for HDLC channels. Another subsystem provides interface to central office switching systems. Lastly, a general purpose computer and file computer system provide for the storage of database and form maintenance functions. Each subsystem is controlled via processor which is linked with each of the other processors by an ethernet local area network. This system provides both Primary Rate (23B+D) and Basic Rate (2B+D) interfaces to the subscribers.

Abstract: This arrangement permits a central processing unit, which can differentiate between code and data fetches, to execute code from any number of pages of data memory without loss of access capability to any of the corresponding pages of program code memory. The page of data memory, corresponding to the program code memory page containing the control transfer programs, may not contain executable programs.

Abstract: This circuit provides for testing the bus structure (address and data buses) of a printed wiring card. This circuit provides an inexpensive means for off line detection of low impedance paths between leads of bus oriented printed wiring cards. This circuit is particularly useful for testing high lead density printed wiring cards, such as, microprocessor or memory related printed wiring cards. This circuit automatically tests all possible combinations of bus leads for a shorted fault condition. This circuit operates without the application of any power to the printed wiring card to be tested. For the detection of any shorted fault leads, the identity of the shorted leads is displayed visually. In addition, for a shorted fault lead, a determination is made as to whether the shorted leads are address bus leads or data bus leads.

Abstract: A method for generating PCM logarithmic values from linear values and storing these values in memory for efficient and rapid data retrieval is shown. This is an off-line method of generating the contents of a programmable read only memory for rapid on-line conversions from linear to logarithmic PCM values by an ISDN system. This method generates either negative or positive PCM values. An initial value and memory address are determined. Next, memory address is incremented and is PCM value decremented. The resulting PCM value is stored at successive locations throughout the memory. Each PCM value comprises a step of a segment. These operations are iterated for each of the segments required for conversion for both positive and negative PCM values.

Abstract: A device for conducting electrostatic potentials to a protection ground is disclosed. The device includes an electrically conductive center section mounted on a substrate mounting device, with the center section electrically connected to the protection ground. First and second arms having an electrically conductive coating extend from opposite sides of the center section. During the installation of a circuit substrate to the substrate mounting device an associated arm is arranged to contact a metalized edge of the circuit substrate providing an electrical path for discharging electrostatic potentials from the circuit substrate to the protection ground.

Abstract: A time shared multiport conference arrangement includes an additive PCM speaker circuit. The additive PCM speaker circuit eliminates the need for loudest speaker detection and the last speaker memory of conventional conferencing arrangements. The additive PCM speaker circuitry operates in an on-line, real time environment to allow rapid summing of speakers' PCM voice samples. Since the PCM voice samples are logarithmic in nature, they are not directly combinable. The additive PCM speaker circuitry provides a storage medium which is preprogrammed with resultant values. These resultant values each correspond to a PCM addition of the values of two input speaker's PCM voice samples. The additive PCM speaker circuit simplifies the complex processing logic usually associated with loudest speaker detection systems and thereby improves the real time operation of the conferencing arrangement.

Abstract: A time shared multiport conference arrangement includes an additive PCM speaker circuit. The additive PCM speaker circuit eliminates the need for loudest speaker detection and the last speaker memory of conventional conferencing arrangements. The additive PCM speaker circuitry operates in an on-line, real time environment to allow rapid conversion and summing of speakers' PCM voice samples. Since the PCM voice samples are logarithmic in nature, they are not directly combinable. The additive PCM speaker circuitry provides for converting the logarithmic PCM signals to linear form. Next, the linear signals of up to three conferees are buffered. Then the speakers' linear form samples are added and each combination reconverted from linear to logarithmic form. The additive PCM speaker circuit simplifies the complex processing logic usually associated with loudest speaker detection systems and thereby improves the real time operation of the conferencing arrangement.

Abstract: A substrate mounting device for installing an electrical substrate to a carrier substrate. The substrate mounting device includes a plurality of tabs extending from the perimeter edges of the electrical substrate. First and second substrate guides are mounted to the carrier substrate and each include a lower shelf and a channel extending longitudinally along a substrate guide inner side, from an open end to a top guide. The channel is further defined by a top surface and a plurality of drop guides which in turn from a plurality of slots. The electrical substrate is installed by manually inserting the electrical substrate into a respective substrate guide open end and manually pushing the electrical substrate along the channels until the electrical substrate encounters a respective top guide whereby, the electrical substrate is urged downward. Each tab then falls within a respective slot, resting the electrical substrate on the lower shelf.

Abstract: A device for conducting electrostatic potentials to a protection ground is disclosed. The device includes an electrically conductive center section mounted on a substrate mounting device, with the center section electrically connected to the protection ground. First and second electrically conductive bands extend from opposite sides of the center section. During the installation of a cirucit substrate to the substrate mounting device an associated band is arranged to contact a metalized edge of the circuit substrate providing an electrical path for discharging electrostatic potentials from the circuit substrate to the protection ground.

Abstract: A laser driver circuit is disclosed for operating an electrical current driven light emitting device or laser. The laser driver circuit is driven from external equipment by a modulated electrical signal and includes a laser biasing network arranged to provide a threshold current to the laser. The current is sufficient to bias the laser to an operating point just below the laser's turn on threshold. First and second transistors connected to the laser form a differential switching amplifier. The differential switching amplifier is disposed to switch drive current provided by a constant current source to the laser. The drive current is sufficient to drive the laser over the threshold set by the laser biasing network. On the application of the modulated electrical signal to the first transistor of the differential switching amplifier the drive current is switched from one side of the differential switching amplifier to the other effectively turning the laser on and off.

Abstract: A substrate mounting device for installing an electrical substrate to a carrier substrate. The substrate mounting device includes a plurality of guide rails mounted on the perimeter edge of the electrical substrate. First and second substrate guides are mounted to the carrier substrate in a spaced and parallel relationship to the other. Each substrate guide includes a channel extending longitudinally along a substrate guide inner side, from an open end to a top guide. The channel is further defined by a top surface and a plurality of drop guides which in turn form a plurality of slots. The electrical substrate is installed by manually inserting the electrical substrate into respective substrate guide open ends and manually pushing the electrical substrate along the channels until the substrate encounters a respective top guide.

Abstract: This circuit converts data in an ISDN data format to data in a T-carrier compatible data format and vice versa. The converted data is then stored in a memory for subsequent transmission. Due to the format differences, the data may be discontinuous. This circuit stores the data in memory in a contiguous fashion to promote and to facilitate the subsequent transmission of the data. This circuit includes a timing and control arrangement which indicates the size of each channel and frame of input data. This circuit generates memory addresses for the storage of both ISDN and T-carrier formatted data which are contiguous over multiple frames of data. A counting arrangement of this circuit converts data received in a modulo 32 format to stored data in a modulo 24 format or vice versa. In addition, this circuit provides output signals for generating proper framing bits and extended superframing information.

Abstract: A process for manufacturing close tolerance thick film resistors on a ceramic dielectric substrate is disclosed. The process includes the steps of printing resistor terminations to the dielectric substrate using a precious conductor material and fixing the resistor terminations by drying and firing in air. A resistive material is next printed to portions of the resistor terminations and to the dielectric substrate intermediate the resistor terminations. The resistive material is fixed by drying and firing in air. Terminal pads, conductor traces and resistor interconnections are printed on the dielectric substrate using a base conductor material. The resistor interconnections are also printed to the resistor terminations and to portions of the resistive material. The terminal pads, conductor traces and resistor interconnections are then air dried and fired in nitrogen.

Abstract: A substrate mounting device for installing an electrical substrate to a carrier substrate. The substrate mounting device includes a plurality of guide rails mounted on the perimeter edge of the electrical substrate. First and second substrate guides are mounted to the carrier substrate in a spaced and parallel relationship to the other. Each substrate guide includes a channel extending longitudinally along a substrate guide inner side, from an open end to a top guide. The channel is further defined by a top surface and a plurality of drop guides which in turn form a plurality of slots. The electrical substrate is installed by manually inserting the electrical substrate into respective substrate guide open ends and manually pushing the electrical substrate along the channels until the substrate encounters a respective top guide.

Abstract: An echo cancellation arrangement is provided for decreasing the "singing" of a connection of a large number of telephone subscribers in a conference calling arrangement. This arrangement includes a means for inserting quiet code during time when the voice samples of incoming PCM data are zero or below a predetermined minimum threshold level. This helps decrease the amount of feedback which is amplified and output through the codec/filter to the listeners through the PCM network. An attenuation arrangement is also included which decreases the level of a summed signal of a summing node of the conference circuit. This sum signal is the combination of each of the conferees' speech. Attenuation of this signal prohibits excessive coupling of amplified feedback to each of the listening conferees.

Abstract: A substrate mounting device for installing an electrical substrate to a carrier substrate. The substrate mounting device includes a plurality of tabs extending from the perimeter edges of the electrical substrate. First and second substrate guides are mounted to the carrier substrate and each include a lower shelf and a channel extending longitudinally along a substrate guide inner side, from an open end to a top guide. The channel is further defined by a top surface and a plurality of drop guides which in turn form a plurality of slots. The electrical substrate is installed by manually inserting the electrical substrate into a respective substrate guide open end and manually pushing the electrical substrate along the channels until the electrical substrate encounters a respective top guide whereby, the electrical substrate is urged downward. Each tab then falls within a respective slot, resting the electrical substrate on the lower shelf.

Abstract: A laser temperature controller is disclosed for controlling the temperature of a laser device. The controller includes a bridge circuit connected to a thermistor device which is mounted on the laser package. The bridge circuit generates error signals representing a need for cooling or heating as the operating temperature of the laser rises or falls about a set threshold. A voltage conversion circuit converts the error signals to a positive or negative polarity voltage. The output of the voltage conversion circuit is applied to a pair of operational amplifiers which input the voltage and compare it to a set reference voltage. When cooling is required a first amplifier provides a biasing voltage to a transistor when a set threshold is exceeded. The associated transistor switches drive current to a thermoelectric device mounted on the laser package thereby, cooling the laser.