Moving along... There is a method/circuit found at airports where pilots tx click radio mics in rapid sequence to turn on night-time runway lights. It's not high security at a locked electric gate but it does work if the secret can be kept under control.
And you wouldn't have to buy/supply dtmf mics. As just a sidebar thought... you could set up a circuit for... say 3 rapid clicks and one or two long clicks to open the gate. I can see that easily being done with some cmos d flip flop logic or a small pic processor if you really were motivated. >> It'll be much more secure than broadcasting tones over the >> company frequency where someone could be listening. Also, >> the garage door openers are short range so that there's >> less chance of an accidental unlocking. > They rejected this idea. They want to use the company radios, > for some reason that I can't figure out. > Joe One other idea I just thought of is simply using a ctcss decoder with a different ctcss on the same channel. No dtmf mic required... just program a second same frequency - different ctcss encode into radio and hit the mic tx button. If you wanted an extra level of security... make it (add) a 3 mic fixed time tx click detect circuit to prevent any false ctcss circuit detects. Or a 3 to 5 second second ctcss long detect-time requirement to fire the gate open controller logic. And... you could offer up the second ctcss decode remote access control from a much more distant user/admin location (a selling feature!) if you use a good receiver on a decent antenna. The key-chain remote control system is probably the most practical and cost effective secure choice for some empire building admin (supervisor) type people . It's often sold by Jameco type places and it's cheap enough. The second ctcss & possible mic click detect circuit simply involves programming a second channel into the user radio and some basic user instruction. (a club to the side of the head until they get it right) I haven't seen much of a generic commercial rough-service dtmf mic that really gets my motor going. cheers, skipp > Actually, they will have to replace all the mikes with TT mikes. > Given the cost of the new mikes and special equipment at the > electric gates, etc, it would be a lot cheaper to go with the > garage door opener style system. Maybe I'll work up an estimate > of what they might spent for both systems and the economics > might help them make a better choice. > joe
