TECH 2: “Automatic telephone exchanges have been invented by the score, but they are likely to be used in practice on a large scale at about the same rate as the automatic motorman and conductor for street cars. The human element will never be gotten rid of in the working of the telephone, but the amount of effort required and the number of steps in handling each connection have been very greatly reduced, as will be shown by a description of the new system.

“The general name under which the new system is known by telephone men is the ‘common battery’ system, a storage battery at the central office being the common source of supply for energizing the transmitters of all the subscribers’ instruments.

“Thus the common battery system does away with the transmitter battery at each subscribers’ station, and consequently with the necessity for frequent inspection and renewal. But it does much more than that for a common source of energy for the whole system, called into play for any particular line only when that line is put in use, permits wonders to be done in the way of signaling. In signaling the central office, the old system required the subscriber to ring the bell, which in turn, threw an indicator on the switchboard in front of the operator enabling her to answer the call. When the conversation was completed a similar ring notified the operator that the parties were through talking.”

More on how it works tomorrow.