Abstract: Electrostatic discharge (ESD) protection for an electrical device is provided through an arrangement which detects an ESD event occurring in the device and reconfigures a processor in the device after the ESD event so that the event is essentially transparent to a user of the device. A detector circuit incorporated into the device detects the occurrence of the ESD event and, in response thereto, generates a trigger signal which is coupled to the processor. Upon receipt of this trigger signal, the processor retrieves status information that is stored in non-volatile memory and was previously contained in a program being executed just prior to the ESD event, reconfigures itself using the status information, and resumes operation with this status information. A data latch connects to the processor and buffers data from this processor to circuitry controlled by the processor.

Abstract: Electrostatic discharge during thermal shock testing on an electronic device (12) by alternate immersion in hot and cold baths (14, 16) of a fully-fluorinated liquid (20) can be reduced by carrying the device within a first, electrically conductive, open-weave basket (32) enclosed within, and coupled to a second basket (30) of similar construction, but a looser weave. The first basket acts as a Faraday shield about the electronic device when both baskets are alternately immersed in the hot and cold baths.

Abstract: In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. An opto-coupled hybrid replaces the port circuit transformer and serves to provide the desired voltage to current conversion. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuits as a voltage where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver via the opto-coupled hybrid. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each port circuit is equal and opposite in magnitude to the voltage generated in the port circuit.

Abstract: A plurality of idle paths through a multistage switching network which are capable of establishing a connection between a particular line and a particular trunk are identified. Repeated selection of paths identified as idle, but actually out-of-service, is avoided by selecting successively different ones of the identified idle paths in a pseudorandom manner to complete the connection between the line and the trunk. The pseudorandom path selection is accomplished in response to predetermined portions of a pseudorandom pattern of binary bits.

Abstract: A monobus conference arrangement is disclosed for use in a key telephone system. A conference circuit is serially inserted on each line and is arranged with an impedance element common to all of the stations using the line. In addition, a monobus circuit replaces the conventional hybrid in each station set. To avoid the problem of having more than one such impedance element connected in a multiline conference, the system is arranged so that current flows in a first direction through the conference circuit associated with the first-connected line and in a reverse direction through subsequently connected line conference circuits. Under control of the reverse current flow, the common impedance elements associated with the reverse current line conference circuits are removed from the connection.

Abstract: In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuit as a voltage where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each line is equal and opposite in magnitude to the voltage generated in the line. In any given line these voltages cancel each other, thereby eliminating the feedback signal.