| 摘要 |
The invention concerns circuit testing devices for connection to an existing electrical circuit to determine whether or not power is present across a pair of conductors. The devices are characterized by having a selector switch which may be placed in either a first position, wherein the device is so connected that an audible signal is emitted only when power is present across the conductors to which the device is connected, and a second position, wherein the audible signal is emitted only when power is not present. The device is disclosed in an embodiment which may be used with either AC or DC circuits, each at various voltage levels, and in a further embodiment wherein the audible alarm is actuated by a radio receiver which receives signals from a transmitter connected to the circuit being tested.
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