Furthermore , the accuracy of the quartz clock superseded the principles of the synchronous motor .
Battery - powered clocks have the obvious advantage of not depending on the proximity of a power outlet , and do not require the often somewhat unattractive electric cable .
The accuracy of the quartz clock superseded the principles of the synchronous motor .
Battery - powered clocks have the obvious advantage of not depending on the proximity of a power outlet , and do not require the often somewhat unattractive electric cable .