A spark gap assembly was developed to protect wide band equipment from improper operation or damage due to fast, high voltage transients that may occur on the coaxial signal cable feeding the equipment. It consists of a commercial fixed, sealed gap mounted in a modified General Radio coaxial tee fitting of either 100 ohms or 50 ohms characteristic impedance. The gaps are presently available from one manufacturer and in voltage breakdown ratings from 350 to 3500 vdc.