Abstract: A multipoint video conferencing system in which the video conferencing terminals are in a daisy-chain arrangement with the head-of-chain terminal connected to the ATM network. ATM cells are relayed from the ATM network downstream to the last terminal, and from each terminal upstream to the network. Each video conference terminal has a video program input port provisioned with a unique ATM address, and a plurality of video program out ports, each provisioned with one of the video program input port addresses. ATM cells generated from each video program input port are transmitted upstream to the ATM network where they are relayed back to the head-of-chain terminal and then downstream to the last terminal. Each video conferencing terminal may also receive ATM cells having addresses that match the addresses provisioned for its video program output ports. These cells are converted to analog video programs and transmitted out the associated video output ports.

Abstract: A circuit for indicating the status of a telephone line at the CPE end, where the status is either on-hook, ringing, or off-hook is disclosed. The telephone line is the normal two-wire telephone line. First, a transconductance amplifier converts a floating voltage difference between the two-wire telephone line into a current. The current is proportional to the voltage difference. Next, a current to voltage converter converts the current from the transconductance amplifier to a single ended ground referenced voltage. The single ended voltage is proportional to the current from the transconductance amplifier, thus the single ended voltage is proportional to the voltage difference across the two-wire telephone line. A voltage controlled switch is turned ON when the single ended voltage is greater than a predefined value indicating the on-hook status. When the single ended voltage is below the predefined value, the voltage switch is turned OFF indicating the off-hook status.

Abstract: A pulse repetition rate check circuit of the type which detects when the second of two consecutive pulses from a pulse generator is early or late with respect to a predetermined repetition time period includes an early pulse detector, first and second early pulse detector enabling means and first and second clocks. Each early pulse detector enabling means enables the early pulse detector responsive to its associated clock for a predetermined time so that a second pulse occurring within the predetermined time is detected as an early second pulse. The early pulse detector enabling means includes an inhibit means for preventing the enabling of the early pulse detector after it has been once enabled.