20mA Current Loop?

General discussions related to the Altair 8800 Clone

20mA Current Loop?

Postby toml_12953 » October 24th, 2014, 10:51 am

The original 2-SIO boards had the option of interfacing with a 20mA current loop device (such as a Teletype). How about adding that optional capability to the ports on the Clone? That would eliminate having to use an RS-232/20mA converter.
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Re: 20mA Current Loop?

Postby AltairClone » October 24th, 2014, 6:45 pm

Sure! Put this inside the Clone instead of inside the Teletype :)

http://altairclone.com/teletype.htm

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Re: 20mA Current Loop?

Postby AltairClone » October 25th, 2014, 11:39 am

Tom, do you have a Teletype? How do you presently have the current loop interface wired? Do you have it terminate in a male DB-25 with pins 2-5 wired as recommended by MITS?

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Re: 20mA Current Loop?

Postby toml_12953 » October 25th, 2014, 12:40 pm

AltairClone wrote:Tom, do you have a Teletype? How do you presently have the current loop interface wired? Do you have it terminate in a male DB-25 with pins 2-5 wired as recommended by MITS?

Mike

I have a Teletype ASR 33 but the interface is terminated by a connector strip with four screw terminals. I could add a DB-25 easily enough, though.

Tom L
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Re: 20mA Current Loop?

Postby toml_12953 » October 25th, 2014, 12:41 pm

AltairClone wrote:Sure! Put this inside the Clone instead of inside the Teletype :)

http://altairclone.com/teletype.htm

Mike


You mean I gotta move all those BYTE magazines outta there?!? :)
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Re: 20mA Current Loop?

Postby AltairClone » October 26th, 2014, 8:12 pm

Regarding an RS-232 interface for the Teletype: How about an "authentic" looking board that fits inside the UCC and has a single connection to the P2 connector on the back of the UCC through which the board obtains power and the transmit/receive current loop signals? No wire cutting, AC adapters, etc. required. RS-232 connection to the board could be through a DB25 connector on the board, or maybe to be a bit more authentic, a three position terminal block?

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Re: 20mA Current Loop?

Postby toml_12953 » October 27th, 2014, 7:26 am

AltairClone wrote:Regarding an RS-232 interface for the Teletype: How about an "authentic" looking board that fits inside the UCC and has a single connection to the P2 connector on the back of the UCC through which the board obtains power and the transmit/receive current loop signals? No wire cutting, AC adapters, etc. required. RS-232 connection to the board could be through a DB25 connector on the board, or maybe to be a bit more authentic, a three position terminal block?

Mike


I'd be satisfied with that! I especially like the fact that it wouldn't require an AC adapter.

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