Abstract: There are two coaxial cable test instruments, of which a primary instrument provides a rump circuit having a battery, a first electric signal device and two probes in series-connection with each other, of which the probes are in the form of the central conductor and surrounding shield parts of a typical coaxial cable connector. The other or secondary instrument provides a second electric signal device which is connected with two further probes in the form of the central conductor and surrounding shield parts of another coaxial cable connector. To test a cable component for a short-circuit, the primary instrument is connected with one of the end connectors of the cable. If the first signal device, for instance a light bulb, then lights up on closure of the rump circuit via the short-circuit bridge between the central conductor and surrounding shield of the cable, the lighted bulb will clearly indicate the short circuit in the cable.