CONQUEST OF DISTANCE BY WIRE TELEPHONY 409 



tion to the work indicated by the ledger numbers listed above. He re- 

 ports as follows: 



During the year a large number of experiments have been conducted 

 with a view to ascertaining the amount of protection to terminal apparatus 

 and the immunity from fire hazard afforded by the present standard pro- 

 tectors. These experiments have shown that, aside from one exception in 

 the case of substation protectors, the present protective apparatus properly 

 installed is capable of furnishing adequate protection to the central office 

 and substation equipment for crosses of any potential. 



With regard to the fire hazard incident to the operation of the protectors, 

 the results obtained from the experiments showed that an appreciable 

 danger from fire existed when the voltage of the circuit crossed with the 

 telephone lead exceeded a certain value. In comparison with the high po- 

 tentials now generally employed by light and power companies, this critical 

 voltage was very low. 



To decrease the hazard of a fire resulting from the operation of the pro- 

 tectors and to secure a substation protector on which the maintenance from 

 lightning would be a minimum, an entirely new system of protection was 

 developed and its elements subjected to these tests included numerous oper- 

 ating trials at the General Electric Company's Works at Lynn, and also 

 two sets of tests at the power house of the New Milford (Connecticut) 

 Power Company. In these latter tests the protective elements were sub- 

 jected to a potential of 33,000 volts under such varying conditions as would 

 be met with in practice. 



In connection with the development of the system of complete protection 

 and in conformity with the results obtained from the tests, the following 

 pieces of apparatus have been designed: 



(1) Substation Protector — providing for open-space cutouts and im- 

 pedance coils — to be used at substations the lines of which are sub- 

 ject to severe static disturbances. 



(2) Outside Fuse — to be used at substations on lines which are exposed 

 to high tension circuits. 



(3) Protector Mounting — to be used in cable boxes where open-space 

 cutouts are required. 



(4) Cable Terminal — provided for open-space cutouts and impedance 

 coils — for use at cable terminals where the entering lines are subject 

 to severe static disturbances. 



(5) Metal Block Arrestor — an open-space cutout for use in connection 

 with 1, 3 and 4. 



These pieces of apparatus have been tested under laboratory conditions 

 and' are now being manufactured by the Western Electric Company. A 

 large number are to be installed by some of the licensee companies and their 



