INSTALLATION OF FIXED EQUIPMEyV 101 



1 EXTENSION BELLS 



Two types are listed as standard equipment by the Forestry Branch. These 

 bells are simply an ordinary polarized ringer inclosed in a suitable box for mounting 

 at any point where it is desirable to receive telephone calls but not necessary to 

 install an instrument. The uses of extension bells are as follows: 



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Fig. 53 Legend 



(1) To enable calls to be received separately from the several lines which ter- 

 minate on a switchboard. 



(2) To enable calls to be received in remote parts of a building or in other 

 buildings at a distance from the telephone instrument. 



(3) To enable calls to be received outdoors at a distance from the telephone 

 instrument. 



Each bell is provided with two terminals and is connected to the line in the 

 same manner as a telephone instrument, that is, on a bridging line it is bridged 

 between line and ground or between the two wires of a metallic circuit. Extension 

 bells must always be protected from lightning and other high-tension currents, as are 

 telephones. 



Extension bells with gongs of different shapes and tones may be secured and 

 are used to make it possible to distinguish signals on different lines from each other. 

 Where different tone bells cannot be secured^ the tone may be altered by placing a 

 wire across the gongs or by sawing a small notch in one or both gongs with a hack- 

 saw. 



2 MULTIPLE LINE SWITCHBOARDS 



It is frequently necessary to install switching stations on long lines in order to 

 keep circuits down to workable lengths. These will usually be placed where a branch 

 makes possible the separation of three lines. The switching method shown in Fig. 54 

 should be used where the three lines are not connected most of the time. It requires 

 the following equipment : Two extension bells, one telephone set, and three single- 

 pole, single-throw, baby knife-switches. With the three lines connected, two exten- 

 sion bells and the telephone remain across the line. 



The method shown in Fig. 55 should be used where the three lines are connected 

 most of the time. It requires the following equipment; Three extension bells, one 



