Abstract: A circuit protection device that can be incorporated into a coaxial cable connector for protecting the circuit from a voltage transient, comprises an annulus 11 that has a central aperture for receiving a central conductor, e.g. pin, of the connector. The annulus is electrically insulating and has a central electrode (12) for connection to the connector pin and a peripheral electrode (14) for connection to the connector housing and the coaxial cable screen. A portion of the electrodes overlie each other and are separated from each other by a layer of semiconductor switching material (16). For example, a chalcogenide glass switching material (16) may be evaporated onto a small projecting area (15) of the central electrode, followed by a small circular area (17) of copper, and the deposited copper area (17) may be wire bonded to the rest of the peripheral electrode (14) by wire bridge (18).