[GreenKeys] [AWA] We have this Model 31 Teletype and need the control box as showen...

[Ralph Mowery]

I don't know about the 20 ma reasoning, but the 60 ma loop is the perferred loop for hams.  That allows the selector magnets to be wired in parallel.  This gives a faster response to the pull in time for them.  It helps to reduce the misprints due to timming problems.

As I said, I don't know anything about the land lines, but I would think that they would want to use a 20 ma loop due to the long wires and less voltage drop with the smaller current.  Maybe someone else can add some insight to this.

Ralph
KU4PT

  ----- Original Message ----- 
  From: Duncan Brown 
  To: antiquewirelessassociation at yahoogroups.com ; cc-awa at yahoogroups.com ; Green Keys 
  Sent: Thursday, November 14, 2013 2:27 PM
  Subject: Re: [GreenKeys] [AWA] We have this Model 31 Teletype and need the control box as showen...


  Most military RTTY used a 20 ma loop. The 60 ma loop was a left over from the telegraph days and when a telegraph or "printing telegraph" had to drive many miles of wire. Most Teletype Corp. M14, 15, & 19 machines would only run on 60ma, so hams were required to stay with the old 60 ma standard.  If you have a TTY only a few feet from the radio, a 20ma loop is sufficient & doesn't require as much power.

  have fun,

  Duncan
  K2OEQ

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