Abstract: A miniature back-up overvoltage protection apparatus for use on an overvoltage protection device includes a housing adapted to be removably mounted on the first and second terminals of an overvoltage protection device. A dielectric is disposed within the housing and is sandwiched between two electrically conducting members done of which is in contact with one end terminal of the overvoltage protection device. A unitary clip is adapted to removable retain the overvoltage protection device and to urge a pair of back-up overvoltage protection apparatuses against the distal terminals of the overvoltage protection device with the clip making electrically conducting contact with the third terminal of the overvoltage protection device, the second conducting member and to the ground terminal of the telephone line system.

Abstract: Gas-filled discharge tube for use as transient protection, with at least two electrodes separated by a discharge gap and an insulating body which is joined to the electrodes and, jointly with them, forms a discharge chamber. The sealing of the tube occurs at atmospheric pressure and a suitable temperature, in a mixture of a light and a heavy gas suitable for the purpose, after which the tube is enveloped in a suitable heavy gas at atmospheric pressure, while the temperature is adjusted in such a manner that the light gas enclosed in the tube, through diffusion and a partial pressure difference, exits through the insulating body, whereas the heavy gases can only to an insignificant degree diffuse through the insulating body. The gas diffusion brings about a reduction in the total gas pressure inside the tube and the process is interrupted when the desired pressure drop is obtained.