File:The Bell System technical journal (1922) (14753554164).jpg

Identifier: bellvol36systemtechni00amerrich (find matches)
Title: The Bell System technical journal
Year: 1922 (1920s)
Authors: American Telephone and Telegraph Company
Subjects: Telecommunication Electric engineering Communication Electronics Science Technology
Publisher: (Short Hills, N.J., etc., American Telephone and Telegraph Co.)
Contributing Library: Prelinger Library
Digitizing Sponsor: Internet Archive

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n Channel regulation was necessary to provide satisfactory transmissionperformance and keep maintenance adjustments to a minimum. Theregulation was designed to compensate for daily and seasonal carriercircuit net loss variations caused by changes in line attenuation withtemperature. It would be desirable to have the terminal regulation rangeequal to 30 db, the maximum line loss that can be spanned between theterminals, to ease engineering layout considerations. However, cost con-siderations led to a 15-db range, with span pads used where required bysystem layout to adjust the received carrier power to the center of therange of the regulator. The regulation in the receiving amplifier is of the backward-actingtype. A reference control signal, derived from the receiving amplifieroutput, is used to vary the loss of the balanced diode variolosser at theamplifier input. The regulator stiffness of 1.6-db change in channelvoice frequency output for 15-db variation in carrier input is obtained
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358 THE TYPE PI CARRIER SYSTEM 359 by the combination of the rectified control signal voltage exceeding thereference voltage of a silicon-aluminum junction diode and by the ex-pansion characteristic of the variolosser. The variolosser uses a speciallycoded set of the silicon diodes which are matched for both ac and dccharacteristics. Modulation products introduced by the variolosser havebeen kept below those produced in the associated receiving demodulator. 3.7 Signaling The need to transmit customer signaling information over a carrierchannel required the development of means of passing dialing and super-vision signals toward the central office. It also required passing ringinginformation to the remote terminal for the types of multiparty ringinggenerally used in the Bell System, including four-party selective service,eight-party semi-selective service and divided code ringing. These requirements were met in such a way that the carrier systemcan be inserted into a normal voice freque

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