Abstract: A HUD for a helmet having an image projector attached to a body and configured to project images. The HUD has a projection optical combiner configured to produce a transparent display of the images. A holder supports the combiner outside the helmet such that the images are visible to a user of the helmet when the head-up display is in use. A forward facing part of the combiner, such as the entire combiner or its forward facing portion, is user replaceable. A system that has the HUD and a spare user replaceable forward facing part and a system having the HUD and the helmet are additionally disclosed.

Abstract: A headset (1) comprises a body (3) and a boom (4), on which a microphone is located. The boom (4) is mounted so that the position of a microphone (5) relative to the body (3) can be adjusted. The headset 1 further comprises a controller (15) arranged to process an electrical signal generated by the microphone (5) by equalizing components corresponding to high and low audio frequencies in accordance with the detected position of the microphone (5). For instance, low frequencies may be preferentially attenuated if the microphone (5) is used when the boom (4) is in a retracted position. Optionally, the controller (15) may also adjust the gain of the microphone (5) in accordance with the position of the microphone (5). The headset (1) may be used to communicate with an external device (2) using a wired or wireless connection. For example, the headset (1) may convey signals to and from a mobile telephone using the Bluetooth® protocol and/or may be used for Push-to-Talk applications.