Abstract: A low power, low cost distributed digital loop (DDL) carrier system that combines television and voice telephone signal transmission over coaxial cables. The DDL system employs a passive/active tap module (114) that controls the steering of the video and telephone signals. The high frequency down stream telephone signal is not processed until a routing terminator (110) converts it to lower frequency signal for transmission in the lower frequency subsplit channel. The telephone signal is then transmitted back up through the subsplit where the active circuitry of each tap intercepts the telephone signal, selects the needed signal and transmits it down to a network interface unit (120) located at the subscriber premises.

Abstract: A call management system connected locally between a central office telephone company switching station (CO) and a conventional single telephone line having multiple extensions provides call paging and intercom capabilities between the multiple telephone extensions. An integrated voltage generator supplies a high voltage, local ringing voltage for ringing the local extensions independent from the CO and a low voltage talk or "battery" feed to the local telephone when they are operated independently from the CO. Line splitting apparatus temporarily separates the CO from the local extensions when the local ringing voltage is generated by the integrated voltage generator and injected into the local telephone extensions. A hold device mimics an active local telephone off the hook, thereby keeping a call from the CO holding when the local telephones are being used in the paging or intercom modes.

Abstract: An improved adaptive echo cancelling system and method is disclosed. The system and method utilizes linear code spacing and is particularly well suited for echo cancellation of full scale signals. Echo cancellation is effected by use of digital-to-analog converters functioning as a multiplier receiving first digital signals representative of a received speech waveform signal and second digital signals representative of the termination network on the line, which termination network causes and defines an echo reflection of the received signal. The output of the multiplier is summed and the sum is then subtracted from the echo components of the received signal to thus achieve echo cancellation and to produce an error signal that is utilized to continuously reduce error between the actual and estimated echo waveforms. Provision is made to inhibit error indications due to circuit generated coding noise and/or predetermined small detected errors to thereby enhance system operation.

Abstract: Disclosed is a centralized circuit for determining whether input signals from a plurality of channels are speech which includes memory means in which digital amplitude samples from each of the input channels are stored in real time. A control means then periodically retrieves the samples from the memory in a time faster than real time and produces a series of time compressed input signals which are compared with a variable threshold derived from a stored level for each channel. Moreover, means are disclosed for setting a new threshold whenever the time compressed input signals differs from the old level for a predetermined time, the new level thereafter being stored in place of the previously stored old level.

Abstract: Disclosed is a circuit for determining whether an incoming signal is a speech signal or a data signal. In the preferred embodiment, means for separating the incoming signal into a low frequency component and a high frequency component are provided. The low frequency component consists of frequencies below a specified frequency, namely 1000 Hz. and the high frequency component consists of frequencies above 1000 Hz. Means are also provided for the comparison of the energy level of the high frequency components with a multiple of the energy level of the low frequency components. Also, means are provided for comparing a multiple of the energy level of the low frequency components with a maximum threshold and for comparing the energy level of the high frequency components with a minimum threshold. Further, means are provided for detecting whether the incoming signal has a slope.

Abstract: The disclosed signal limiting circuit is bridged on to a bidirectional communication path (T, R) and functions to selectively attenuate excessive signals (2V.sub.A) being transmitted in a predetermined direction on the bidirectional communication path. This is accomplished by a signal discriminator circuit (100) which separates the excessive signal (2V.sub.A) from the plurality of signals appearing on the communication path (T, R). The signal discriminator circuit (100) also inverts the isolated excessive signal, passes it through an attenuator (102) to a signal injection circuit (103) which injects a controlled amount of the 180 degrees out-of-phase isolated excessive signal back on the communication path (T, R) to cancel out a portion of the excessive signal, thereby providing selective attenuation of the excessive signal.

Abstract: Circuitry useful in PCM coders for effectively shifting the idle channel noise signal to a level midway between the code state boundaries thereby significantly reducing the likelihood that noise signals will cross a boundary and be encoded.

Abstract: In a time assignment speech interpolation system, a fixed delay between the input speech channel and the transmission facility provides time to generate and transmit a symbol representing the speech channel to which the transmission facility has been assigned. At the remote location, a fixed delay between the transmission facility and the output speech channel provides time in which to detect the symbol and perform the necessary switching.

Abstract: A circuit for converting an input analog signal into a digital representation and a remainder signal is disclosed. The digital representation is generated by a coder that counts an integral number of clock cycles during an interval in which the magnitude of the input analog signal is compared with the magnitude of a ramp signal. The remainder signal is generated by duration-to-amplitude conversion of a pulse whose duration is the fractional remainder of the final uncounted clock cycle.

Abstract: An arrangement for controlling the d.c. state of a subscriber's loop which has a port appearance in a time division switching network is disclosed. Because such a network provides no metallic path between the subscriber's line port and the trunk circuit, the abandonment of the call by the trunk circuit must be detected by a trunk scanner rather than by the line circuit directly and conventionally, a processor operation being required to interpret the scanner information. Heretofore a complex subscriber line circuit would have been required to respond to the processor operation so as to inform the station user that the call has been remotely abandoned. The present arrangement allows the processor to reoperate the ringing relay in the subscriber's line circuit during an interval when the group of line circuits including that of the affected subscriber would not normally receive active ringing.