Abstract: A fire alarm system having increased immunity to false alarms comprises control and indicating means (6) and a plurality of ionization smoke detectors (7) connected through signal lines (8, 9, 14) with the control and indicating means (6), each ionization smoke detector (7) comprising an ionization measurement chamber (1) for producing an electrical signal having a characteristic indicative of a monitored condition, a radioactive source (10) to ionize the air in the ionization measurement chamber (1), and an evaluation circuit comprising an amplifier element (3) to amplify the electrical signal from the ionization measurement chamber (1), threshold detection means (15, 16) for comparing the electrical signal characteristic to minimum and maximum limits and for producing an alarm or trouble signal, and electronic means (5, 11) by which the chamber voltage (UK) of the ionization measurement chamber (1) is increased as far as possible to the saturation range of the ionization chamber (1) if the ionization curren

Abstract: A connection apparatus for a fire alarm is composed of a socket portion intended to be secured in the space or area which is to be monitored and a fire alarm insert connectable by means of electrical and mechanical connection elements with the socket portion. At least three connection elements are arranged about the circumference of the socket portion. At the circumference of the side of the fire alarm insert confronting the socket portion there are provided contact springs. The connection elements and grooves come into engagement with one another in a certain manner. During a first partial rotation of the fire alarm insert there is established the mechanical connection. During a subsequent second partial rotation of the fire alarm insert, in the same direction as the first partial rotation, there is established the electrical connection.