Abstract: Method and apparatus for selecting a single telephone line from among multiple line pairs at a location remote from the central office and isolating that line from the respective subscriber line to allow the performance of line tests on same. Line pairs are sampled sequentially for a short time interval to determine whether a signal is present within an initial detection band, that band having a range about .+-.100 hz of the test signal frequency. If a signal is found, the system shifts to a validation made to defect a signal within a range of about .+-.10 hz of the test signal frequency during a preselected long time interval. Upon finding a signal present at the end of the validation cycle, the system disconnects the selected line from its respective subscriber line and begins performing line tests to diagnose problems.

Abstract: An apparatus adapted to be coupled into a party telephone line for selecting a ringing signal transmitted on the line from among a plurality of possible coded ringing signals that could be transmitted on the line and for coupling the ringing signal to a telephone is disclosed. The apparatus comprises a rectifier coupled to the party line for providing a rectified ringing signal, a first switch having the rectified signal as an input for reversing the polarity of the rectified signal at selected times, a second switch coupled to the first switch for selecting either the rectified ringing signal or the ringing signal itself and a third switch coupled to the second switch for coupling the selected signal to a telephone coupled to the third switch.

Abstract: An apparatus and method for sensing a predetermined tone signal transmitted on a transmission line, such as a telephone transmission line, and for generating a signal indicating the presence of the tone signal. The apparatus comprises a tone detector circuit including an amplifier, bandpass filter and comparator, a power supply for generating power for the detector circuit from a voltage present on the transmission line and logic circuitry for gating pulses of power from the power supply to the detector circuit on a periodic basis thereby to enable the detector circuit to check for the presence of the tone signal during the durations of the power pulses.

Abstract: Method and apparatus for selecting a single telephone line from among multiple line pairs at a location remote from the central office and isolating that line from the respective subscriber line to allow the performance of line tests on same. Line pairs are sampled sequentially for a short time interval of about 35 ms to determine whether a signal is present within an initial detection band, that band having a range about .+-.100 hz of the test signal frequency. If a signal is found, the system shifts to a validation mode to detect a signal within a range of about .+-.10 hz of the test signal frequency during a preselected long time interval. The system remains in validation mode for about six iterations of the validation routine, each long time interval being about 0.5 seconds duration. Upon finding a signal present at the end of each such validation cycle, the system disconnects the selected line from its respective subscriber line and begins performing line tests to diagnose problems.

Abstract: A telephone line testing circuit for determining whether a fault exists on a telephone line entering a customer's premises or whether the fault exits in the customer's wiring and equipment. The testing circuit comprises a test switch, a polarity detector, a current detector, a dial tone detector and an indicator. The polarity, current and dial tone of an incoming telephone line signal are tested sequentially in the same circuit and in one operation such that if any one of the three characteristics of the entering telephone line contains a fault, the indicator will not generate a signal. When the entering telephone line signal has the correct operating polarity, sufficient operating current draw and a dial tone of the correct operating frequency, the indicator will generate a signal indicating that no fault exits on the entering telephone line.

Abstract: Apparatus is disclosed for disconnecting and reconnecting equipment to a telephone line in response to at least one AC signal sent over the telephone line. The equipment can automatically be reconnected after a predetermined time period, or reconnected only after another AC signal is received. The apparatus includes digital circuits for detecting a signal within a predetermined frequency range which is present uninterrupted for a minimum time period to activate switching. The apparatus also includes digital timing circuits which can provide relatively long time periods during which the equipment is disconnected which do not utilize large energy storage devices. The digital circuits of the apparatus are operable at extremely low currents, e.g. less than 30 ua total drain. The regulator utilizes one or more light-emitting diodes drawing a current of only about 5 ua to generate a reference voltage.