| 摘要 |
<p>An electrical system which comprises a temperaturesensitive device comprising a PTC or NTC element, a load in series with the temperature-sensitive device and a control device in parallel with the load and the temperaturesensitive device. The control device is a device whose resistance can be changed from a high value (which may be infinite) to a low value or vice versa, by a change in the electrical or physical environment thereof, e.g. a diode, triac, thyristor, PTC device or NTC device. By an appropriate change in the power source, e.g. its size or direction, or in the physical environment of the control device, e.g. its temperature, the relative resistances of the temperaturesensitive device and the control device can be reversed, thereby isolating or activating the load. The system is particularly useful for isolating a remote load, e.g. a telephone, while retaining a continuous circuit e.g. through the legs of a telephone circuit, for example for test purposes.</p> |
