Permissible to use DTMF on amateur bands to control a gate?

Discussion in 'General Technical Questions and Answers' started by KJ4CAY, Jul 1, 2020.

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  1. KJ4CAY

    KJ4CAY Ham Member QRZ Page

    Is it permissible to use DTMF tones to control a gate opener on one's property,

    and by extension, is it permissible to use rolling DTMF codes (codebook-style) for security?

    and, would the gate have to identify itself, if the equipment connected to the gate only passively listens for the tones?
    Last edited: Jul 1, 2020
  2. WR2E

    WR2E Ham Member QRZ Page

    @KJ4CAY Without reading into the rules, I would say yes...

    Since radio control of model airplanes and boats is permitted, why would radio control of a gate NOT be permitted?

    I believe you would need to use frequencies that are permitted for this... maybe VHF only? (looks like 6 meters only?)

    No... if the gate is a receiver only, it would not have to identify itself. In fact, I'm not even sure that the transmitter would have to. I don't believe the transmitters for R/C hobby have IDs in them, but I could be wrong about that.

    I'm curious why you would consider this when there are commercially available equipment already on the market for the purpose?
    Last edited: Jul 1, 2020
  3. KJ4CAY

    KJ4CAY Ham Member QRZ Page

    I think in the case of RC models, a flag on the antenna's controller satisfies that requirement.

    In the case of rolling the DTMF codes over, I'm concerned that may be considered some type of cipher.
  4. K3XR

    K3XR Ham Member QRZ Page

    It's not clear from your post if you intend to perform this function on a ham radio frequency. If it's the case I would assume you have already reviewed Part 97 of the rules and regulations before asking the question. In case you haven't you might want to take a look at :
    §97.113 Prohibited transmissions.
    §97.119 Station identification.

    Anyone is free to listen to any transmission on the ham bands. It's not about the reception of signals.
    KB0MNM likes this.
  5. KJ4CAY

    KJ4CAY Ham Member QRZ Page

    I have and it isn't clear to me if this is permitted, esp. in the case of using a rolling code or code book with the DTMF tones.
  6. W1BR

    W1BR Premium Subscriber QRZ Page

  7. WR2E

    WR2E Ham Member QRZ Page

    I think there are also R/C freqs in the 72MHz band non-licensed...

    (never mind, I see they are mentioned in the article you linked!)

    Although something stands out in those freq lists... they are specifically talking about VEHICLES. Nothing about remote controlling 'other' stuff. I wonder if that makes a difference.

    and then of course the 315MHz freqs for commercial garage door and gate openers.
    Last edited: Jul 1, 2020
  8. K8JD

    K8JD Ham Member QRZ Page

    Sure looks like a 6M freq in the proper segment of the band, can use as remote control but you have to have an ID device in the transmitter,
  9. W1VT

    W1VT Ham Member QRZ Page

    §97.215 Telecommand of model craft.

    An amateur station transmitting signals to control a model craft may be operated as follows:

    (a) The station identification procedure is not required for transmissions directed only to the model craft, provided that a label indicating the station call sign and the station licensee's name and address is affixed to the station transmitter.

    (b) The control signals are not considered codes or ciphers intended to obscure the meaning of the communication.

    (c) The transmitter power must not exceed 1 W.

    [54 FR 25857, June 20, 1989, as amended at 56 FR 56171, Nov. 1, 1991][/QUOTE]
  10. AG6QR

    AG6QR Premium Subscriber QRZ Page

    The word used in Part 97 is "telecommand". It appears in several places in the rules, including 97.211, 97.213, and 97.215.

    If you want to telecommand a space station, an amateur station on or within 50km of the Earth's surface, or a model craft, that's clearly allowed, subject to the applicable rules. But a gate is none of those.

    If you want to telecommand something else, it's not clear to me. 97.111(b)(3) authorizes telecommand one-way transmissions, without specifying what sort of device must be controlled. 97.3(a)(4) defines telecommand as a one-way transmissions to initiate, modify, or terminate functions of a device at a distance.

    My reading of it, which shouldn't be trusted, is that if you want to control a gate, you may do so, but you don't get the exemption from ID requirements that you'd get with telecommand of a model craft, nor do you get the exemption from encoded messages to obscure meaning that you'd get with telecommand of a space station.

    Regardless, as a practical matter, I think I'd probably do this using unlicensed Part 95 gear, rather than using Part 97. That would avoid legal ambiguities, and it would work well enough.
    W6KCS likes this.

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