Abstract: An alarm system suitable for use in a telecommunications network in which a central switching system is capable of selectively providing a signal of a predetermined polarity to a plurality of remotely located stations without being dependent upon or impeding the ability of the central switching system to process relatively high volume communications traffic. Each of the remote stations is connected to the telecommunications network by an electrical conduction path. The stations are substantially unresponsive to the predetermined polarity signal. In response to an alarm indication signal, the system effects a reversal in the polarity of the signal provided to a selected subset of the remote stations. Each station in the selected subset responds to the polarity reversal by indicating an alarm condition.

Abstract: A telephone line card tester operates by transmitting test data to the digital port of a telephone line interface card, and by subsequently receiving the data which is transmitted from this card through the same digital port. Once received, the data pattern is compared with an expected data pattern. A difference between the received data and the expected data is indicative of a defect in the telephone line interface card. To meet telephone line interface card timing consideration, the transmission of data to the interface card and the analysis of data received from the card are performed by separate subsystems. To accomplish this task, the telephone line interface card is tested in a test fixture which includes a digital line interface card tester, and a communications test set. The communications test set is used for such functions as ring generation and line simulation.

Abstract: Multiple electrical path assembly as in a telephone grid, is rapidly and accurately checked by grounding one end of all but one of the path conductors, applying a test signal to that one end, detecting the presence or absence of signal on both ends of all conductors, and repeating the procedure for all the conductors, as with a computer containing a microprocessor. Where the conductors are individually switched, they can all be switched on beforehand. Detectors can also be connected to the conductors during the testing, to detect unusually high voltages, and testing can be interrupted when such voltages are detected. Switch actuation can be separately tested by detecting the passage of current that is used to actuate them.

Abstract: Multiple electrical path assembly as in a telephone grid, is rapidly and accurately checked by grounding one end of all but one of the path conductors, applying a test signal to that one end, detecting the presence or absence of signal on both ends of all conductors, and repeating the procedure for all the conductors, as with a computer containing a microprocessor. Where the conductors are individually switched, they can all be switched on beforehand. Detectors can also be connected to the conductors during the testing, to detect unusually high voltages, and testing can be interrupted when such voltages are detected. Switch actuation can be separately tested by detecting the passage of current that is used to actuate them.