[aprssig] Mic-E and HTs
zl1vfo at yahoo.co.uk
Mon Dec 12 23:48:46 CST 2005
<http://www.byonics.com/tinytrak/tinytrak3.zip> --> TinyTrak3_Schematic.png
The Tinytrak3 senses the PTT in line from the microphone via D5 and
pin 11 (RB5). When the line goes from low to high, it knows that the
operator has just released the PTT button, so it outputs a high on pin
1 (RA2), turning on Q1, and pulls down the PTT line again, so it can add
it's (TT3) data burst on the end of the over. (Mic-E PTT action, as
opposed to a Mic-E compressed packet.)
D6 is there to stop it retriggering itself.
> From: Wes Johnston <aprs at kd4rdb.com>
> Subject: Re: [aprssig] Mic-E and HTs
> To: TAPR APRS Mailing List <aprssig at lists.tapr.org>, Scott Miller
> Ahhh.... but perhaps Scott is talking bout the tiny track _sensing_ the
> mic line. First it has to sense what the status of PTT is so that it
> can know when you release PTT so it can inject the packet.
> Wouldn't this be an integrating op amp? Just bypass any frequency above
> 100hz, right?
> Stephen H. Smith wrote:
>> scott at opentrac.org wrote:
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