I too had a clifford installed by the dealer on my old car. It was a dealer purchased unit but after doing some snooping myself came to find out that it was the same as a clifford concept 400 without the proxy sensor installed.
A DVM is a Digital Multi Meter. (some installers will call it a DVM because they only measure DC voltage) basicly takeing the place of your old analog multimeters. And no this isn't a cliffNet interface cable.
Most of your car/audio shops that have sold cliffords in the past will still have this cable around and maybee even the cliffnet wizard installed on their shop PC. You can do a couple things if you wish to stick with the clifford unit. Go to a local shop that sells clifford and they will charge anywhere from 10 - 40 $ to program or re-program your unit. or attempt to find the cable or make your own. IT's not easy to make your own and getting the pinout correct can be difficult if you don't have the right equipment.
Basicly it is a straight through serial cable. I wish I could give you the pinout, but I don't remember! I made my old cable by taking a old CD-ROM audio card cable that so happened to fit exactly into the clifford Brain unit and extending it with 24awg wire putting a DB9 end on the serial cable.
Her's the deal with the clifford alarms retair or dealer purchased. The input for the cliffnet wizard cable is on the brain of the unit and the cable plugs dirrectly into the brain. It has been a few years since I used this setup. I'm not a clifford fan by any means and unless this has changes since DEI purchased clifford the dealer is feading you lines when they indicated that they installed the input for the cliffnet wizard cable. As far as I know their is no difference between the dealer models and the retail models. (all camd from the same factory).
As far as the 1/8" cable input that audio speaks of this is the antenna input on the older models. ( don't know if this is still the case on the newer alarms. Wasn't on mine. this is your standard stereo headphone jack size but I believe they used male RCA wich is not 1/8" ?. I don't believe they have gone to using this for the input for the newer cliffords , but could be wrong here.
In fact, I would ditch the clifford. I had my old unit in for repair more that it was in my car. Also to add to that the dealer did such a poor job installing it. I had completely removed the unit and cable harness because it was causing too many issue. I am not a clifford fan nor would I suggest even screwing with the clifford units. Many will aggree and many will disagree. Don't forget that not too long ago clifford went bankrupt and was bought out by DEI so DEI actually makes the new clifford units under the old name and the older ones that are still in stock are still sold.
Not sure if this helps you out at all. But thought I'd let you know of my past experience with my clifford unit.