Abstract: A communications system is described which comprises a transmission unit including a transmission circuit 12 operable to output a transmission signal to a ground antenna 22 driven, in use, into a ground formation, and an impedance adjusting unit 20 electrically connected between the transmission circuit 12 and the antenna 22 and operable to adjust the transmission output impedance. A ground antenna 22 is also described comprising a single rod or stake including a first active section 30, a second active section 32 spaced apart from the first section 30 and collinear or coaxial therewith, and an insulating section 34 located between the first and second sections 30, 32, holding the first and second sections 30, 32 in a spaced, collinear or coaxial relationship.

Abstract: A communications system is described which comprises a transmission unit including a transmission circuit 12 operable to output a transmission signal to a ground antenna 22 driven, in use, into a ground formation, and an impedance adjusting unit 20 electrically connected between the transmission circuit 12 and the antenna 22 and operable to adjust the transmission output impedance. A ground antenna 22 is also described comprising a single rod or stake including a first active section 30, a second active section 32 spaced apart from the first section 30 and collinear or coaxial therewith, and an insulating section 34 located between the first and second sections 30, 32, holding the first and second sections 30, 32 in a spaced, collinear or coaxial relationship.

Abstract: A protection device comprises a covering including at least a layer of ballistics material, and a layer of an electromagnetic screening material.

Abstract: A protection device comprises a covering including at least a layer of ballistics material, and a layer of an electromagnetic screening material.

Abstract: A glass window pane breaking device comprises a suction pad for attaching the device to the window, in use, a striker rod with a breaker tip, a trigger pawl engagable with the striker rod and a remotely operable trigger which is biased normally to prevent movement of the trigger pawl and thus to retain its engagement with the striker rod when this is held against the force of charged energy storage means urging the breaker tip in a direction to break the window pane, in use. A switch is also provided to ‘arm’ the device or place it in a ‘safe’ mode.