Take a panel or box and attach every type of connector you commonly use to it in pairs.
IE: 2 mono 1/4" jacks, 2 1/4" stereo Jacks, 2 RCA jacks, etc. You get the idea.
Now you will need a pilot light socket for every conductor of the jacks. Put a pilot light socket in SERIES with one of leads coming from the connector. Install a 6.3V pilot light in the socket. Off one side of the other connection to the pilot light, again in series, put a 6.3V fil transformer or wall wart, and install a fuse in the secondary and a power switch in the primary. Fuse the secondary so that it is about 1/8 amp larger than the pilot light draws. This protects the transformer against shorts. You can also use batteries, but a 150 ma or larger pilot lamp is essential.
When you plug in a cable to test continunity you can wiggle the cable and see if the light goes out. If so, the cable has a
short or open in it.
Many commercial units only use LED's, but they will not truly tell you if you have a high resistance/ marginal connection, due to the fact an LED draws practically no current. A real pilot lamp will, due to its higher current draw.
You can test practically any cable you may run across with this device. (Yes, a IDE 50 connector will require 50 pilot lamps, etc.) Most of us typically would use it for coax and stereo cable continunity.
I have also built these units specifically for computer cables using the LED's to test everything from the 2 pin header conn to the IDE 50 conn, including cat 5 conn and telephone conn. Some even had selector switches and LED's that would tell you exactly which line in a cable was shorted to what other line. Sort of a "must have" back in the days of the S100 computers when you assembled the cables by hand. (I just wished I had patented the unit I originally built, as a year later somebody else did).