> "rtc_0001" <[EMAIL PROTECTED]> wrote: > If you build a ptt counter, bear in mind that commercial units > offer a programmable window of opportunity within which your ptt's > must arrive or the system resets. The usual windows are setup for > 1 ptt per second for the number of ptts necessary. If any of the > ptts arrive outside that window, you have to start over.
> Other than the rather pricey (for this job) S-Com units, I don't > know who else makes such a device commercially. The Hamtronics dtmf decoder board (with latching logic) has an auto patch (telephone) valid dtmf password sequencer circuit that is pretty much the circuit we're talking about. A string of cmos flip flops and a simple rc timer do the job real well. Instead of valid dtmf digits... you simply use the ctcss or cos logic as the valid data input. One of the advantages of kit building... good circuits can be adapted to other projects/tasks. cheers, skipp
