Abstract: A surveillance device, e.g. a fire alarm or an intrusion detector, includes a mount having a connector block, and an insert having a sensor assembly, a printed circuit board with evaluation electronics, and an electrical contact to the connector block. The printed circuit board is a plug-in card with a contact strip. For insertion, with the mount disposed at a horizontal surface, for example, the insert is first moved vertically and then displaced horizontally. In the horizontal displacement, an electrical connection is established between the contact strip and the connector block.

Abstract: Upon insertion of a fire alarm insert into a corresponding fire alarm mounting, the insert covers the mounting. The insert has a movable fastening comprising a ring, for example, for fastening the insert to the mounting. Indicator elements are included for indicating proper positioning of the insert relative to the mounting.

Abstract: Due to aging of the insulating materials arranged between the electrodes in ionization fire alarms or detectors the insulating efficiency of these thus formed so-called insulating paths or spans deteriorates in the course of time despite, or maybe even due to the cleaning operations performed upon such ionization fire alarms. To ensure that the insulating capacity does not fall below a critical value the insulating path or span is formed by at least two different insulating materials. The materials are arranged in such a manner that the creepage path between the electrodes extends across all the different insulating materials. This principle also may be applied to other measuring devices which require a high input resistance of an amplifier stage.

Abstract: A gas sensing unit designed to be protected against explosions and serving for the detection of combustible gases in an atmosphere, containing a gas sensor functioning according to the principle of catalytic oxidation or a semiconductor gas sensor. The gas sensing unit contains, within a housing, at least two mutually separated chambers or spaces. The one chambr is a compression-proof space and contains an electronic evaluation circuit for the gas sensor, the other chamber, which is a space structured to be protected against explosions, contains the gas sensor and a balancing element and is separated from the atmosphere by a sintered metal bushing or sleeve. A third explosion-proof chamber or space can be provided in the gas sensing unit for the purpose of connecting the lines or conductors. The gas sensor together with the balancing adapter forms an assembly or unit which can be pluggably arranged in the cover of the chamber containing the electronic system or hardware.

Abstract: An ionization chamber of the type used in an ionization smoke detector is made adjustable. The chamber has two electrodes and one radioactive source for ionizing the electrode gap. One of the electrodes is laterally displaceable relative to the other. As a result of displacement of this electrode, areas of the electrode with differing geometrical configurations can be brought into the ionization zone of the radioactive source.Several different embodiments of the electrode with different geometrical configurations are described.

Abstract: To permit separation of a fire sensor element from a socket element, but prevent accidental, or unauthorized removal and separation, the socket element is formed with a movable catch engaging in an opening or recess in the sensor element, upon moving the sensor in engaged position with respect to the socket. The catch can be released from engaged position only by a removal tool pressing the catch out of engagement, the removal tool preferably being so constructed that it surrounds the sensor element to inhibit contact of the person handling the removal tool with the sensor element, and thus prevent contamination of the sensor element, or injury to the operator if the sensor element contains dangerous materials.