File:The Bell System technical journal (1922) (14569462577).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

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
cannot be used on the same pole line, because certain frequencies wouldbe used for both directions of transmission. This would produce largedifferences between transmitted and received carrier power at terminalsand repeaters which would lead to intolerable crosstalk. A number of terminal arrangements were studied in order to implementthe above frequency plan. The arrangement for a remote terminal shownin Fig. 2 was chosen as the simplest terminal meeting all of the systemrequirements. It is very similar to the channel terminal arrangementused in the Type Nl carrier system, another double sideband amplitudemodulation sj^stem used for long distance trunks of the Bell System. Theseveral shaded portions in the figure show the breakdown of the terminalfunctions into individual sub-units, which are the basis for the equipmentarrangements discussed in Section 5 of this paper. A number of the otherimportant features that make up the terminal arrangement are discussedin the following sections.

Image Captions:

Fig.2 — P1 Carrier remote terminal block diagram.

Text Appearing After Image:
a3d o cc O IJ LU UJ 2 (J) U 354 THE TYPE PI CARRIER SYSTEM 355 3.2 Use of Transistors Transistors were chosen for use in the PI system because they are lowvoltage, low power devices as compared to electron tubes suitable fortransmission circuitry. Also, transistors are expected to be lower in costand inherently longer life devices than electron tubes, thus contributingto reduced initial and operating costs. The dc power requirements for the PI system, using transistors, maybe compared to those for a channel terminal in the Type Nl system asan indication of the dc power saving that has been achieved with thePi system. A transistorized PI terminal requires about 1.2 watts whileit is in operation compared to 40 watts required for an Nl terminal, INPUT

Note About Images