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Nokia Bagphone

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  • dantemclean <dantemclean@hotmail.com>
    Hello: Once again, I m here posting for help on a strange idea. I have an old Nokia bagphone, C15 handset, which uses the C250-MKII transceiver unit. I use
    Message 1 of 1 , Dec 7, 2002
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      Once again, I'm here posting for help on a strange idea.

      I have an old Nokia bagphone, C15 handset, which uses the C250-MKII
      transceiver unit. I use this phone both in the car, and on the
      sailboat, and simply put, 3 watts of power can't be beat! It also has
      the advantage of locating the antenna unit away from the user.
      However, I have one problem with the phone. I don't have the handsfree
      option kit.

      I know there was a handsfree conversion kit for the bagphone, and from
      what I can gather, this involved a "craddle unit" which was plugged
      into the RJxx connection coming out of the handset and had a connection
      of the same nature which went to the transceiver, and a lavalier
      microphone with a 3.5mm male miniplug on it (I assume this plugged into
      the craddle). Having taken the handset apart, I found the following;
      that the mic output seems to go directly into the handset cable. That
      the speaker goes through a bunch of resistors on the board, and then (I
      assume) to the coiled handset cable--I had some trouble tracing this
      circuit around the board. That there is a magnetic reed switch on the
      board, which was actuated by a magnet in the craddle unit. This would
      have told the phone that it was "hung up" and that it should use the
      external speaker instead of the internal one. Picking up the handset
      would probably have switched out of handsfree mode, and into "privacy
      handset mode." A software setting configured the phone for "H/F
      Present" or "H/F Not Present."

      So, it would seem to me that by splicing two 3.5mm jacks into the
      thing, one for the mic, and one for the speaker, and by using jacks
      such as those used in computers, which shutoff the internal speaker
      when headphones/external speakers are connected, I could implement the
      same thing as the craddle unit used to. And by simply putting a small
      magnet on the handset, I could activate the reed switch--making the
      unit think it is on a craddle, which also seems to change it over to
      DTMF tones via speaker, instead of simple key press beeps via ringer.
      In my case, I plan to use a casette adapter for the "speaker" unit.

      I don't care about not having a "privacy handset mode." Nor do I care
      that this isn't exactly a "new" phone. I want handsfree, I don't need
      "voice activated" dialing, or whatever. I can pull over to dial, and I
      usually pull over to talk too.

      However, before I get too far into this, I would like to confirm theory
      and wire tracing with actual pin assignment information for the handset
      cable, and impedance information too (if possible). Does anyone have
      this information, or know of any source besides Nokia?

      Thanks for any suggestions/help. I know this idea is not terribly far
      fetched, it is just a question of which wires to use.

      Dante McLean
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