Abstract: A waveform generator for generating a desired waveform is provided, including a noise kernel configured to store a plurality of samples from a predetermined waveform, the plurality of samples being assigned to a plurality of memory blocks; and an address arrangement configured to randomly select a selected one of the plurality of memory blocks; wherein the noise kernel is configured to communicate the plurality of samples assigned to the selected memory block.

Abstract: A waveform generator for generating a desired waveform is provided, including a noise kernel configured to store a plurality of samples from a predetermined waveform, the plurality of samples being assigned to a plurality of memory blocks; and an address arrangement configured to randomly select a selected one of the plurality of memory blocks; wherein the noise kernel is configured to communicate the plurality of samples assigned to the selected memory block.

Abstract: An adapter for interconnecting a tip-ring telephone, a PBX telephone, and a private branch exchange (PBX) is configured to pass out-of-band signals between the PBX telephone and the PBX and to attenuate voice-band signals therebetween when the tip-ring telephone is being used. The adapter includes a band-reject filter and a switching mechanism for connecting the band-reject filter between the PBX telephone and the tip-ring telephone.

Abstract: A digitally programmable attenuator balances impedance across a two to four-wire hybrid to reduce echo. The hybrid can interface a two-wire bi-directional telephone line, used for both transmit and receive signals with four-wire circuits having separate unidirectional transmit and receive signal paths. The four-wire circuit interfaces the two-wire circuit through a transformer. Optimum isolation is obtained by setting impedance Z.sub.BAL equal to the impedance of the line including the transformer (Z.sub.LINE). The invention eliminates manual or customized individual adjustment of Z.sub.BAL by a set up technician by use of a digitally controlled attenuator to electronically vary the value of Z.sub.BAL in a highly precise fashion. The programmable attenuator provides an input voltage to a buffer voltage-follower amplifier. The output of the follower amplifier is coupled to a known impedance to limit current flow through the impedance and consequently, current flow through Z.sub.BAL.

Abstract: First and second ISDN modems are disposed at a subscriber location and telephone system central office and are arranged to operate in a normal mode, and in a bypass mode upon power failure at the subscriber location. The modems are coupled through the telephone lines via interface transformers having centertaps. The centertap at the subscriber location is split and coupled to a sealing current source and that at the central office is coupled to a sealing current detector and ground. Sealing current flows between the respective transformers during normal operation. A drop in sealing current due to subscriber power failure is sensed at the central office, causing local logic to bypass the central office interface transformer and to couple the central office voice switch directly to the telephone lines. Loop current detectors at the subscriber location and at the central office determine whether the subscriber location voice telephone device is on-hook.

Abstract: A time division multiplexer is operable to sample data on parallel input channels at a sampling rate at least twice the data rate, to serially transmit the data for each channel in a respective time division, and to recover the data at a receive end. The multiplexer is provided with a bit storage register for successive samples on at least one input channel to be used as a marker channel. Gating connected to the bit storage register forces a detectable unnatural data pattern on the transmitted data for that channel whenever a predetermined bit pattern is stored for that channel. According to one embodiment, when a plurality of unchanged levels (e.g., binary one) appear in the bit storage register, a central bit is inverted to thereby mark that channel. The inverted marker bit is detected and cancelled at the receive end and/or is used to reset the channel counter if detected on a channel other than the marker channel.