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.