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| TELEPHONE - WALL TERMINAL-STATION TELEPHONE FOR TRUNK LINE WORK
No. 320 A key for short-circuiting the bell, when a signal is given, and the induction coil, when listening, is fitted. This prevents noise in the neighbourhood of the instrument from being heard, and also reduces the resistance, which will be found an advantage oil long lines. The key is to be pressed down when listening only, and not when talking. Some practice will be required in order to get the full advantage of this arrangement, but it is, of course, by no means necessary to use it under ordinary circumstances. The instrument is fitted with a Paper clip instead of the writing table shown on the figure. Weight 20.5 lbs. Price £4 1 0s. Renumbered as the AB 500. |
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Last revised: March 28, 2024FM2 |
This instrument is of the
large size and fitted with transmitter No. 570, receiver No. 546 with cord No.
2030, four-magnet generator No. 479 which will ring satisfactorily through the
300 ohm bell of the instrument and a line resistance of 25,000 ohms; a battery
box to accommodate two large Leclanche cells No. 586 or dry cells No. 971 is also included.