300SDL Mysterious Black Box

I recently bought an '87 300SDL. When I removed the lower cushion of the back seat to treat the leather, I discovered a black metal box lying on the soundproofing on the driver's
side. It's black and measures about 3 x 7 x 1.5 inches; there are two cables running from the box into the trunk area. It isn't secured to the car.
There's of those helical cellular telephone antennas mounted at the top of the rear window, and between that and the fact that this box says "Motorola" on it, I thought at first that it might be an amplifier for a built-in cell phone the car might once have had. But then I realized that there are no wires running forward from the box toward the front seat area.
Anybody have any idea what this thing is?
Geoff
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snipped-for-privacy@u1.netgate.net (Geoff Miller) wrote:

<tin foil>There are listening devices in the seat cushions!</tin foil>
Honesty, though, that sounds like a very unusual thing. Have you been able to trace the wires to anything? I don't believe they had keyless-entry systems back then, though it may have been an add-on alarm system...but I can't imagine it'd be under the seat.
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Heh...
The car does have a factory keyless-entry system, as a matter of fact. (And I wish it didn't; not only is it an unnecessary complication, but that chirping when I lock and unlock the car is annoying as hell. I wonder if there's some way to disable the audio.) But even so, I can't imagine why the control unit for it would be under the back seat.
Thanks, Geoff
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Geoff Miller wrote:

My w124 has its central locking vacuum pump under the backseats (on th eright hand side), encased in some padding. I added an aftermarket remote control to it. Guess where I put it? Right, under the backseats...
I got this RC unit (no chirping, I hate that too):
http://www.produktinfo.conrad.com/datenblaetter/850000-874999/854688-an-01-de-Funkfernbedienung_MT-150_MB2.pdf
Ximinez
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It might be an amplifier for the radio antenna's signal.
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Could very well be. The car has an aftermarket Alpine stereo (although I also have the Becker that came with the car), so maybe that was put in at the same time.
Thanks, Geoff
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Cell phone box. I think it is the "standard" equipment added on by the dealer then. My 87 300SDL has that too, at the same location. The cell phone itself is not as big as a brick but is more than the usual house phone. No one uses such kind anymore so the previous owner may have taken out it with the wiring. Does the center console has 2-3 screw holes on the passenger side, just about where the knee is?
If you are interested to reconnect it, I can give my phone to you :-)
Geoff Miller wrote:

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No; I just went outside and looked. I suppose it's possible that the original owner had the console replaced because of the unsightly holes left by the removal of the phone, but that would've been a pretty expen- sive fix for something rather trivial.
I have the window sticker, and there's nothing on there about a phone. The only listed option is the sunroof, which I didn't realize was optional.

Heh...thanks for the offer, but I think I'll stick with my StarTac. ;-)
(I'm in the "go out to the driveway and stare at it in disbelief" phase of new car ownership. I can't believe I actually own one of these beasts at last. It positively *dwarfs* my W124 300D 2.5, which I park next to it. The sensation of size and mass reminds me of the '65 Buick Wildcat that a friend of mine drove in high school.)
Cheers, Geoff
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It is probably a 3 watt phone that was installed in the early 1990s. Does it have a 25 pin connector and a chrome plated RF screw on connector? My guess is the handset has been removed long ago. Most carriers will not activate a phone this age due to GPS requirements on new phones.
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