. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. 344 BELL SYSTEM TECHNICAL JOURNAL best adjustment and the most desirable circuit condition for the operation of a relay or similar device. With the bridge, this requires very little time, especially since the results of the individual measure- ments are immediately available to guide the work. With the oscillo- graph, several hours may be required and the results obtained are available only after developing and analyzing the oscillograms. The calibration of the bridge
. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. 344 BELL SYSTEM TECHNICAL JOURNAL best adjustment and the most desirable circuit condition for the operation of a relay or similar device. With the bridge, this requires very little time, especially since the results of the individual measure- ments are immediately available to guide the work. With the oscillo- graph, several hours may be required and the results obtained are available only after developing and analyzing the oscillograms. The calibration of the bridge is determined by the values of certain capacities and resistances in the measuring circuit. These may usually be selected with sufficient accuracy during manufacture so that the bridge requires no further calibration after it has been constructed. In fact, it has been found practicable to design the bridge so that the steps on a standard decade resistance box correspond to decimal fractions of a second. Jl f °V\MaAM/o-. Fig. 1 The principles underlying the measurement of an interval of time will be explained in connection with Fig. 1. Two condensers Ci and C^ of unequal capacity are charged from a common battery Bz. The condenser Ci, which has a larger capacity than C2, is charged through an adjustable high resistance R\ during the time elapsing between the operation of relay W and the subsequent operation of relay X. This elapsed time is the interval of time to be measured and the charge accumulated on the condenser is an accurate means for doing so. The second condenser C-> is used merely for comparison purposes. It is charged through a fairly low resistance Ri and acquires its full charge in a relatively small interval of time. After the completion of the charging interval, relay Y is operated and the two condensers are discharged simultaneously through a differential meter circuit. If the two charges are equal, the meter will show no deflection, but if they are unequal,
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