[GreenKeys] Model 15-A?

[Bob Camp]

Hi

I guess I'll jump in here and get a few of the basics covered. I'm 
going to *assume* we are talking about a model 15 teletype and not 
something else.

A model 15 has been one of the staple items on the used Teletype market 
since WW2. A fairly typical land line hookup would consist of a 
printer, a keyboard, a local loop supply (say 125VDC at 60 ma) and a 
polar relay. The polar relay would hook to the wire line and convert 
the polar "telegraph" signals to the on/off pulses that the Teletype 
understands.

Physically the 15 has three basic pieces. There's the printer / 
keyboard, the table (usually metal) and the loop supply box. Whole 
thing is maybe four feet tall by two feet by two feet. Black is a 
common color as is green.

Now for the fun part. The machines don't always run at the same speed. 
They pretty much use the same code(s) but they run at different words 
per minute. In order to get them to talk to each other you need both of 
them to be running at the same speed. The second thing is that the 
RS-232 output of your 300 baud modem isn't quite up to driving a 125 
volt / 60 ma local loop. That part is easy to fix with a simple keyer 
board.

What you are suggesting is fairly straightforward to do. The equipment 
is available and hooking it up is not a "rocket science" sort of thing. 
If you need more equipment the main issue is that it's big and heavy. 
Packing it for shipment is a pain ....

	Take Care!

		Bob Camp
		KB8TQ


On Feb 9, 2005, at 11:47 PM, Derek Cohn/WB0TUA wrote:

> Dear Friends,
>
> I am a non-tty guy who is thinking about taking the plunge.  I was 
> recently offered a teletype with a cryptic description "15-A".  Is 
> that a standard Model 15 or possibly something else?  Apparently there 
> are several items that come in the package (perhaps loop supply, 
> terminal unit, etc.).
>
> Anyway, my primary interest is in landline Morse (railroad Morse) and 
> I am active on the Morse Telegraph Club's dial-up telegraph circuit.  
> We use old 300 baud modems to FSK into a "hub" where up to 6 operators 
> can telegraph.  We transmit a "mark" and "space" over the phone lines 
> and a converter to generate a voltage to operate our telegraph 
> instruments at each end.
>
> When I was discussing the teletype this evening on our virtual 
> telegraph wire, I discovered that one of our group members, a retired 
> AT&T technician, has a teletype that he would like to put on our 
> telegraph wire if he can find another person who would be interested.  
> It stands to reason that we can subsitute the teletype for our hand 
> keys or bugs and use the teletype to key our circuit.
>
> I'm curious if anyone has ever done something like this before.  
> Looking forward to hearing from you guys!  Also...is there anyone in 
> the St. Louis, MO area who is familiar with mechanical teletypes that 
> could serve as an Elmer as I try to get this project going?
>
> Thanks,
>
> Derek Cohn
> Morse Telegraph Club - Alton Chapter
> Office UD, Sine DJ
> Amateur Radio Station - WB0TUA
> 1969 Brunswick M274A5 Mechanical Mule
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