POWER PLANTS FOR TELEPHONE OFFICES 721 



With regard to types of batteries, the enclosed type in glass jars will 

 be increasingly introduced wherever suitable because of the lower cost 

 of installation and the subsequent reduced maintenance. The further 

 extension of continuous floating systems of operation also makes it 

 practicable in some cases to use batteries of the pasted plate con- 

 struction in hard rubber jars, which are cheaper, particularly in first 

 cost. On the general subject of battery operation, the use of the 

 "continuous floating system" is being encouraged where practicable 

 since this usually gives more efficient operation and always results in 

 longer life for the storage batteries and in smaller sizes for equivalent 

 reserve. As an alternate plan a "constant voltage charge system" is 

 in process of adoption for general use where, for any reason, continuous 

 floating is impossible or uneconomical. 



The size and cost of power plants is largely controlled by the circuit 

 and apparatus requirements, and improvements in these, such as 

 reductions in current drains for dial equipment and for repeater tubes, 

 are immediately reflected in the telephone power plant which will 

 decrease in size and cost in almost direct proportion. 



