Abstract: In a cable restoration system neon devices and light-emitting diodes are utilized to identify corresponding conductors in a broken cable by an arrangement that does not require the assistance of a lineman at the central office. The apparatus identifies a central office line by means of a neon device and ringing bridge arrangement which replaces the neon indicating bulbs used in prior art systems. After identifying a customer line at a cable break by using indicating devices in a conventional manner, a maintenance man at the break location dials the central office over a spare pair. When ringing is applied to the desired central office line, a glow discharge occurs in the neon device, which discharge heats a bi-metallic strip and causes the strip to move and establish a metallic short across the line. The short trips ringing extinguishing the discharge. The bi-metallic strip cools and the short is removed from the line.
Type:
Grant
Filed:
March 27, 1975
Date of Patent:
September 14, 1976
Assignee:
American Telephone and Telegraph Company
Abstract: In pulse amplitude modulated time division switching systems, noise and crosstalk often result because the time division switches used to connect individual channels to a common bus are not perfect open circuits when they are in the off-state. The switches in the off-state possess a small parasitic capacitance which couples energy on the common bus to the channel resulting in a noise signal during time slots which are not associated with the channel. A method is disclosed for substantially reducing crosstalk and noise induced by stray capacitances without increasing the complexity of the time division switch. Each pulse on the common bus is converted into a bipolar pulse in which positive and negative portions have equal average values. In addition, the timing of each of the time division switches is modified to extract the desired signal by sampling the first portion of the bipolar pulse in the appropriate time slot for that channel, and rejecting the second portion of the bipolar pulse.
Type:
Grant
Filed:
August 2, 1974
Date of Patent:
March 9, 1976
Assignee:
Bell Telephone Laboratories Incorporated