Motor Dictograph

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    Is anyone familiar with the Motor Dictograph intercom system found in limousines?  My 1933 1236 EDL has a speaker over the driver’s seat, in the headliner, so the vehicle must have come with an intercom system.  Before I got the car, I understand the interior was burned out, so I can see where some items may have been lost in the restoration.  A clock over the divider window was upholstered over, but has now been replaced, and the intercom seems to be the last item on the car I need to tackle.  The Motor Dictograph was not exclusive to Pierce, but could be found in most of the high end limousines of the era, including European makes.  I know that some installations had a panel at face level by the right rear passenger set, with a microphone, and a push button in the armrest next to the ashtray to speak to the driver.  Note, speak to, not with, as it was one way conversation.  My car, being of six window design, doesn’t seem to have room to have a face level microphone in the headliner, so I have to assume it had a hand held microphone.  I was able to get the cable retractor for a microphone from Chris Diekman, but had no luck finding a microphone on eBay and such.  Had the brilliant idea of contacting the Illinois Antique Radio Association, and wound up with three, two kind of ratty and one perfect one.  I should be able to pick up the braid covered cord without any problem.

    Looking again on eBay, I have seen some older systems, and they seem to have only two components, the microphone, and the receiver for the driver.  I would almost think that there would be some kind of amplifying unit between the two.  Does anyone have one of these systems in their limousine?  Right now, the interior of my car, which was  very faithfully redone, gives no hint.  I don’t want to start ripping up the headliner on a wild goose chase.  I’m going to pull the speaker over the driver in the hope of finding some wires connected and try to find the same pair behind the back seat, but does anyone have any first hand experience on these systems?  Couldn’t find anything in the Service Bulletins.




    From what I can ascertain (my big word for the day), the system is simply the carbon microphone and diaphragm speaker wired in series with the battery.  It’s a two wire system, power line to microphone, microphone out to speaker, speaker to ground.

    It would be easy enough to test if microphone and speaker are out of car.  It may also be possible to snake wires under rear carpet and up rear armrest, so there’s no tearing out of interior.

    fun stuff… David Coco Winchester Va


    Thanks David, that’s along the lines of what I was thinking.  Right now, the car is still at CPS getting the finishing tounches done on the right front door lock, and I hope to have the car home this week.  I can easily remove the speaker and test it with the microphone.

    Got the radio installed and working, turn signals, rear clock, and now I’m getting excited again about the car after this spring and summertime funk due to the Corona Virus.  Really hoping for a good year next year.

    Thanks again,



    My 1703 EDL has an intercom. The power from the pushbutton goes to a terminal on the mic. There are three wires from the mic to the speaker. Happily, there are numbers at the terminals that correspond to numbered terminals on the speaker. The speaker frame is connected to the ground wires for the dome light and clock to complete the circuit. Frequently, all that is needed to make this system work is tapping the carbon mike on a wooden workbench to loosen caked carbon granules. Tap firmly but take care not to fracture the potmetal case. Good Luck!

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