Device for monitoring telephone terminals for faults, in particular short circuit

摘要

In a device for monitoring one or more terminals which are connected to the telephone network for faults, in particular short circuit, each loop to be monitored is provided with a normally disabled contact breaker which is enabled when a fault occurs. In order to prevent external activation and exclude inadvertent de-activation, it is proposed to form the monitoring circuit power supply from a storage capacitor which can be charged alternately from two sources, of which the first source is enabled only at the beginning for a short period within which a storage capacitor is charged which supplies a control mechanism and monitoring device in the different loops with operating voltage. Both sources are supplied with power from the main connection line. Through the de-activation of the first source, a series resistor is bypassed which would prevent the normal operation of the telephone device. However, the second source is then available which is connected to the other main connection wire and which ensures the provision of the further operating voltage via a contactless electronic switch when this line is successfully de-activated.