[GreenKeys] Silent 700 Terminal with a 43 TTY (TDU) ?

Thu Apr 11 12:15:19 EDT 2013

Ya...  I think you'd still have trouble.  Cross connect would allow an
electrical connection between two modems IF they were direct connect
(ie, have a DAA).  Acoustic coupled units will need a telephone handset
added to the equation...   but you will still have the wrong tones.

Two originate modems can't talk to each other.   You can only talk
originate to answer because of the tone pairs used in each direction.
It's key to remember that these were duplex connections too...  data was
moving inbound at the same time it was moving outbound and so they had to
keep the transmit FSK pairs from interfering with the receive FSK pairs.

For reference,

http://en.wikipedia.org/wiki/Bell_103_modem

"The originating station used a mark tone of 1,270 Hz and a space tone
of 1,070 Hz."

"The answering station used a mark tone of 2,225 Hz and a space tone of
2,025 Hz"

In other words,

originate modem		answer modem
---------------		------------
send 1070/1270		listen 1070/1270
listen 2025/2225	send 2025/2225

So, the Silent 700 or M43 with either direct connect or acoustically
coupled modem is going to send to and listen from an answer modem peer.
It won't hear an originate modem used as a peer.

Therefore, I think you have to get at them before the modem and make
your connection to the serial interface there with either 20mA or RS232.

There were Bell 103 modems (both direct connect and acoustically coupled)
that were switchable between originate and answer mode to solve this
very problem but I do not believe those were normally built into the
two terminals being discussed here.

Chris N0JCF

On Wednesday (04/10/2013 at 01:57PM -0700), Michael O'Day wrote:
> Chris' description of the "originate" modem setup kicked loose an old Dust Bunny of a memory. We used to have to connect leased line modems together (at 1800 baud) to test our equipment in order to determine if comm problems were internal or external. One FE had a "Ma Bell" cable, complete with D-blocks, that would cross connect the modems. We would be monitor the RS-232 signals to verify everything was working.
> Could you use a similar setup to connect the Silent 700 to the model 43?  If needed you could run the signals through an isolating interface using an opto-isolater chip to avoid voltage level conflicts. We used to connect TD-830 data terminals to loop current driven dot matrix printers the same way (the isolator circuit was built into the printer), and never had a problem.
> 
> 
>  
> Mike - N9ODM
> 
> 
> ASCII and ye shall receive.
> 
> 
> 
> ________________________________
>  From: Chris Elmquist <chrise at pobox.com>
> To: greenkeys at mailman.qth.net 
> Sent: Wednesday, April 10, 2013 12:25 PM
> Subject: Re: [GreenKeys] Silent 700 Terminal with a 43 TTY (TDU) ?
>  
> Yes... roger that.  I keep a couple TI Silent 700's running and indeed
> you can get "thermal fax paper" at most office supply stores.  The rolls
> are smaller (ie, less paper) than OEM but it is the same kind of paper
> and works well.
> 
> As for connecting a model 43 to a Silent 700 using the "phone plug",
> I think you might have trouble.   If it is a phone plug for connecting
> to the telephone network, then it's very likely that it has an internal
> "originate" modem with DAA in it.  The Silent 700 might have an acoustic
> coupler too and that would also be an originate modem.
> 
> These two modems won't talk to each other because they are both using
> originate tones.  You need an answer mode modem to accept the call from
> the terminal(s) and use the opposite tone pairs for each direction not
> to mention getting from the acoustic coupler on one to the direct connect
> modem on the other.
> 
> Your best hope would be to find the serial data on some connector or
> port before it goes to the modem.  I am not aware of any Silent 700 that
> had 20mA and all those I ever saw were RS232.   So, if you can find an
> RS232 connection on the M43 and also on the '700, this would be the way
> to connect them together.
> 
> My 725 and 745 models do 110, 150 and 300 baud...  7 bits, selectable
> even/odd parity and I would guess the M43 can be set to match one or
> all of these modes as well and then you should just need three wires--
> Tx, Rx and GND to hook them together...  but I realize there's a lot of
> handwaving and what-if there since we don't know much about the interface
> capabilities of either machine.
> 
> Chris N0JCF
> 
> 
> On Tuesday (04/09/2013 at 08:30PM -0500), Sherry Guttery wrote:
> > On 4/9/2013 5:56 PM, Richard Schumann wrote:
> > >Wow...can you still get thermal paper to fit those?
> > I am not sure if your looking for 98' roll of Thermal paper, but if
> > the kind and size you need is 8.5" x 98' x 1/2" core it can still be
> > ordered from Staples or similar approximately $18.99 for a 6 pack.
> > >
> > >    ----- Original Message -----
> > >    *From:* Norm <mailto:normand3 at q.com>
> > >    *To:* greenkeys at mailman.qth.net
> > >    <mailto:greenkeys at mailman.qth.net>
> > >    *Sent:* Tuesday, April 09, 2013 1:49 PM
> > >    *Subject:* [GreenKeys] Silent 700 Terminal with a 43
> > >    TTY (TDU) ?
> > >
> > >    Hi
> > >    The Question today for me, will a Silent 700 Terminal
> > >    work back to back with a  model 43 TTY equipt with
> > >    aTerminal Data Unit (TDU)  that has the phone plug?
> > >    Thanks
> > >    Norm
> > >    WB7WEQ
> > >
> > >
> > >
> > >______________________________________________________________
> > >GreenKeys mailing list
> > >Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> > >Help: http://mailman.qth.net/mmfaq.htm
> > >Post: mailto:GreenKeys at mailman.qth.net
> > >
> > >This list hosted by: http://www.qsl.net
> > >Please help support this email list: http://www.qsl.net/donate.html
> > 
> > 
> > -- 
> > sherry guttery
> > 
> > A Tender Tale - a page dedicated to those Ships and Crews
> > so vital to the United States Silent Service: In Memoriam / Randy Guttery
> > http://tendertale.com
> > 
> > ______________________________________________________________
> > GreenKeys mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:GreenKeys at mailman.qth.net
> > 
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> 
> -- 
> Chris Elmquist
> 
> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

> ______________________________________________________________
> GreenKeys mailing list
> Home: http://mailman.qth.net/mailman/listinfo/greenkeys
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:GreenKeys at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

-- 
Chris Elmquist