A balance system detects ferrous or non-ferrous metallic objects carried by people or present in certain articles. This balance consists in the generation of a fixed oblique magnetic field of detection, substantially constant, whatever the orientation or positioning of the objects to be detected in the search area. The balance in combination with a search gate, includes a transmitting coil and a receiving coil, each having an L-shape, inverted relative to each other.

A fault indicator apparatus employs a single indicating device such as a light emitting diode (LED) to provide an indication of all zones within a plurality of zones which exhibit a predetermined condition being monitored. In particular, the invention is employed in a multi-zone intrusion system where a single indicator provides an output indicative of all zones which are not secure. The apparatus causes the indicator to blink the zone numbers in a continuous sequence and for example, if zones 2 and 5 were not secure the indicator would provide two flashes indicative of zone 2 and then provide a predetermined pause while then providing 5 flashes indicative of zone 5. The user by counting the flashes can then immediately determine which zones in the plurality of zones have been violated.

The invention is directed to a status-reporting device with a plurality of sensors which send output signals whose values depend on the status monitored by the sensors and with an evaluating device which is connected to the sensors and responds by sending an alarm signal when a preselected value of the output signals is reached. According to the invention, the evaluating device has an individual threshold switch (IC.sub.51) which generates the alarm signal and is connected with the output (3) of an interrogating device (IC.sub.3) which has a plurality of inputs (1, 2, 5, 12-15) connected to each sensor, respectively, and means (IC.sub.2) which connect the inputs (1, 2, 5, 12-15) with the output (3) periodically and one after the other. Also described is a temperature sensor which is particularly suitable for fire detection and fire extinguishing systems, as well as a process for the production thereof (FIG. 4).

When one of the failure detecting devices disposed at some spots in an electronic appliance detects failure of the electronic appliance, the failure detecting device detecting the failure generates a certain voltage. From the voltage, a certain specific voltage of good stability is generated as a first information indicating the occurrence of a failure in electronic appliance, and a second information is generated indicating place of failure. A means is provided for generating voltage, or data, which contains the elements of both first and second informations. Based on the voltage, or data, generated from the means, a place of failure is specified and displayed.

Gauges for indicating the level of sensed parameters are often provided in connection with a variety of machines. Advantageously, such gauges are sufficiently flexible to indicate the level of a parameter having a warning level that is dependent upon the level of a second sensed parameter. In the subject invention, a gauge indicates the level of a primary sensed parameter having a normal operating range. A sensor produces a signal indicative of the level of a secondary sensed parameter and the levels of the primary sensed parameter associated with the normal operating range are modified in response to the level of the secondary sensed parameter.