As most of you are probably aware the BFD and Teradek units use the exact same power connector but they are wired with polarity reversed from each other. And if you use the wrong cable the BFD analog receiver (not the digital) and the Teradek units get damaged. Today I sold a BFD to someone who had a bunch of cables and wanted to know how to tell them apart BEFORE she plugged them into the units and risked damage. My first thought was to recommend getting a voltmeter but trying to get probes on the pins is difficult and risks shorting out the cable. I have a simple cable tester I use but it isn't something you can just buy.
Then I had a brainstorm: You DO have a cable tester already: It is your BFD handset! Just remove the 9V battery and plug the power cable into the POWER IN jack on the base of the unit. If it turns on your cable is good for use with the BFD. If it doesn't it is either broken or reverse polarity. Unlike the receiver the handset has reverse polarity protection so you won't risk damaging the handset.
It's that simple. But you MUST REMOVE THE 9V BATTERY FIRST. It won't damage the handset or the battery if you don't but it will power the handset even if the cable is bad so it can give a false positive.
I hope this helps you out in the field. Spread the word!