. Bell telephone magazine . nd. If a voltage is built up onthe wires, due either to lightning orthe presence of some other source offoreign potential, it breaks across thesmall gap between the carbon blocksand escapes to ground. Such highpotentials are thus diverted from thecentral office equipment. A peakvoltage of about 450 volts betweenline wires and ground is required, onthe average, to break down the pro-tectors in this manner (minimum ofabout 350, maximum of about 575volts). When high earth potentialsexist, the protector blocks operate ina reverse manner. In this case a highpotential bet
. Bell telephone magazine . nd. If a voltage is built up onthe wires, due either to lightning orthe presence of some other source offoreign potential, it breaks across thesmall gap between the carbon blocksand escapes to ground. Such highpotentials are thus diverted from thecentral office equipment. A peakvoltage of about 450 volts betweenline wires and ground is required, onthe average, to break down the pro-tectors in this manner (minimum ofabout 350, maximum of about 575volts). When high earth potentialsexist, the protector blocks operate ina reverse manner. In this case a highpotential between points A and B,which may be represented by abattery connected between the twogrounded blocks as shown in Figure3, will break across to the blocks con-nected to the line wires. Dependingupon the particular circuit terminat-ing conditions, the breakdown of gapsdue to ground potential requires onthe average about 450 volts and inmany cases as much as 750 volts, par-ticularly when two sets of protectorblocks are in NAVAI. OBREBVtS March 21 March 22 FIG. 4 Sun spots: Photographs of the solar disc on six days last March March 25 What Happened on March 24 JjUT now, let us return to a consid-eration of what occurred on March24. Magnetic records made at theUnited States Coast and Geodetic Ob-servatory at Cheltenham, Maryland,show that the storm began at 8 (Eastern Standard Time) March24. At 10:45 an unusually vio-lent period began, reaching its maxi-mum about 12:00 noon and continu-ing until about 2:00 A high de-gree of magnetic activity persisteduntil about 9:00 on March displays of aurora borealiswere seen on the night of March 24,being visible as far south as Tucson,Arizona. A moderately large groupof sun spots was present on the cen-tral disc of the sun during the can be seen from Figure 4,which is a succession of photographstaken of the solar disc on days justbefore and just after the period ofgreatest disturbance. Reports f
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Keywords: ., bookauthoramerican, bookcentury1900, bookdecade1920, bookyear1922
