[GreenKeys] USB-teletype adapter with ASR33 question

[Lester Veenstra]

Transmit loop is dry contacts so it does not care. The 20/60 ma question is
a matter internal to the USB adaptor.

Lester B Veenstra  MØYCM K1YCM W8YCM
lester at veenstras.com

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-----Original Message-----
From: epvgk at limpoc.com [mailto:epvgk at limpoc.com] 
Sent: Tuesday, June 07, 2016 5:01 PM
To: Lester Veenstra
Cc: 'Julien Scrofani'; greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] USB-teletype adapter with ASR33 question

On Tue, Jun 07, 2016 at 04:58:57PM -0400, Lester Veenstra wrote:
> Put a low voltage power supply and current limiting resistor (No need for
130 V in this case) in series with the ASR TX contacts and the USB input.
Set up the voltage/resister for 60 MA and you should be in business.  Before
you start, put an ohm meter across the ASR TX contacts and you should see a
fairly low resistance.  When typing you should see the resistance go up.

He's using a 33, shouldn't it be 20mA? (the usb adapter won't care, but the
tty
might?)

eric

> 
>  
> 
> Lester B Veenstra  M??YCM K1YCM W8YCM
> 
>  <mailto:lester at veenstras.com> lester at veenstras.com
> 
>  
> 
> Physical and US Postal Addresses
> 
> 5 Shrine Club Drive (Physical)
> 
> 452 Stable Ln (RFD USPS Mail)
> 
> Keyser WV 26726
> 
> GPS: 39.336826 N  78.982287 W (Google)
> 
> GPS: 39.33682 N  78.9823741 W (GPSDO)
> 
>  
> 
>  
> 
> Telephones:
> 
> Home:                     +1-304-289-6057
> 
> US cell                    +1-304-790-9192 
> 
> UK cell                    +44-(0)7849-248-749 
> 
> Guam Cell:              +1-671-929-8141
> 
> Jamaica:                 +1-876-456-8898 
> 
>  
> 
> This e-mail and any documents attached hereto contain confidential or
> privileged information. The information is intended to be for use only by
the individual or entity to whom they are addressed. If you are not the
intended recipient or the person responsible for delivering the e-mail to
the intended recipient, be aware that any disclosure, copying, distribution
or use of the contents of this e-mail or any documents attached hereto is
prohibited.
> 
>  
> 
> From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of
Julien Scrofani
> Sent: Tuesday, June 07, 2016 4:29 PM
> To: greenkeys at mailman.qth.net
> Subject: [GreenKeys] USB-teletype adapter with ASR33 question
> 
>  
> 
> Hi all,
> 
>  
> 
> I bought Eric's usb adapter to link my asr33 tty to a PC.
> 
> As is, I can transfer from PC to the tty but I cannot transmit in the
other way, tty toward PC.
> 
>  
> 
> I know that current loops are needed. 
> 
> It works for one way without additionnal power supply, so maybe my 33 has
an internal current loop. My problem is I'm not able to determine if it's
really the case and I don't how to add one if I need to.
> 
>  
> 
> I have no electronic knowledge at all, sorry if my question is a dummy one
!
> 
> Thank you in advance.
> 
>  
> 
> Bests regards, 
> 
> Julien
> 

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