Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems (1921)
Smith, Arthur Bessey, b. 1875, Campbell, Wilson Lee · New York : McGraw-Hill · leaf 166
Fig. 144.—Thousand lines being expanded. on the second selectors that they formerly occupied on the first selectors.The new numbers for these subscribers will be the old numbers with thefirst digit doubled. Thus, 245 will become 2245, etc. The remaininglevels of the newly installed second selectors… … Fia. 145.—Fourth selectors for party lines in 5-digit system. The next step in growth is to open a new thousand on some otherlevel of first selectors, exactly as was done on the second level illustrated.In this way, level after level may be expanded until it is a 10,000-linesystem. As the system…
Telephone
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