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Phone/radio interconnect control

Discussion in 'Hobby Electronics' started by Jim, Sep 11, 2004.

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  1. Jim

    Jim Guest

    Thanks for reading and apologies for being so vague.

    I have a phone/radio interconnect that relies on the phone user switching
    the rx and tx by using the dtmf tones on a handset (* and # from memory).
    Just wondering if I can supply the tones to the interconnect as the phone
    user or radio user talks.
    Any ideas of how I might go about this gratefully accepted.

  2. Alan

    Alan Guest

    You don't say whether it is for VHF/UHF or HF use.

    Commonly on VHF/UHF the switching is controlled by the RX squelch
    line. When the mobile talks it cuts off the speech from the line.

    The TARA and the TACT both use the squelch line.

    On HF it is normally the voice on the telephone line which operates a
    VOX type switching arrangement, but you have to be careful that the
    VOX isn't operated by the received audio from the RX.

    The Codan/IPC 500 telephone interconnect uses a hybrid transformer
    which is balanced to the line conditions at the beginning of the call.

    The Barrett 660/960 telephone interconnect uses a hands free telephone
    type IC to split the telephone line into TX and RX components.

    The above is very basic but might give you some ideas.


    Jenal Communications
    Manufacturers and Suppliers of HF Selcall
    P O Box 1108, Morley, WA, 6943
    Tel: +61 8 9370 5533 Fax +61 8 9467 6146
    Web Site:
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