Abstract: An alarm device is disclosed for use with a fire detector which emits a visual or audible signal having recognisable characteristics. The signal is picked up by the alarm device which includes discriminating circuitry can recognise the signal. The device further includes a sound bomb which is activated upon a recognised signal being picked up. In a fire alarm installation there can be a series of alarm devices each of which recognises the signal of another alarm device whereby a number of alarm devices are activated in sequence.