[GreenKeys] AutoStart

[Steve Garrison]

But it doesn't have to be associated with a TU at all!

A long time member of this group designed and built a motor control board based on a 555 timer controlled through an opto-isolator that used the loop current to 'measure' the length of the marking current after characters stopped coming in.  After an adjustable length of time with no start bit, the circuit would "time out" and open the contacts on a relay, that controlled the AC to the motor.  Then when the first start bit was received the circuit was reset and the relay closed thus turning on the motor.   I have recreated a new version of Jack Hart's, K2TTY, board and if I ever get around to assembling the ones I promised to other's of our group, I'll probably make another run of boards.

Steve G./N4TTY

-----Original Message-----
From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net> On Behalf Of jim at k6ccc.org
Sent: Tuesday, August 31, 2021 4:47 PM
To: Greenkeys <greenkeys at mailman.qth.net>
Subject: Re: [GreenKeys] AutoStart

From: "steve bennett via GreenKeys"
> How does autostart work?Is that functionality built into the teletype 
>machine or is it done  in a TU or somewhere else?

In it's simplest form, it's a function of the TU.  The TU decodes Mark tone, or Space tone, or both to determine that there is a valid signal and then turns on AC power to the TTY.

When valid signal goes away, the AC power is killed to the TTY.

73
-----
Jim Walls - K6CCC
jim at k6ccc.org


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