[GreenKeys] i-Telex Coming Soon to N4TTY QTH

[COURYHOUSE at aol.com]

ok... but I  am sure although there is  some weird   wiring,  there is no 
call control unit on this  19.
Ed#
 
 
In a message dated 11/20/2016 9:06:39 A.M. US Mountain Standard Time,  
jdangus at att.net writes:

On 11/20/2016 9:43 AM, COURYHOUSE at aol.com wrote:


ok without the call control unit  is that  still a problem  to  on / off  
the
machines  or  has that   been  taken care of?

The way a call control unit interfaces with the TW39 line is dependent  on
two things. Line current and polarity.

A minimum "idle" current  of 5-7 mA to show the machine is there.
Increasing the current to 40 mA is  "off hook"
Once that far connection has been made, the polarity reverses  to
show it it connected (and starts the machine motor via a relay.)
For  incoming calls, the polarity reverses, the call control unit increases
the  line current to 40 mA and starts the motor via a relay.

The simple  method, but requires a bit of board surgery, is to jumper the
polarity  relay and use the polarity relay control signal to close a motor/
machine  power replay.

Setting a command on the TW39 board allows for dialing  via the key-
board rather than requiring a pulse type dial in series with  the line.

It still requires changing (shorting out) an additional  resistor in the 
local
loop to increase the current from 7 mA to 40 mA.  Typically a 6200 ohm
resistor.

The call control units do this all  automatically. 

The TW39 cards on the i-Telex "box" do all the work to  emulate a TW39
central office connection to the local loop (usually) via a  call control 
unit.








-- 

Jeff-1.0

wa6fwi

_http://www.foxsmercantile.com_ (http://www.foxsmercantile.com/) 


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