Re: HP 3081a ASCII terminals help


Paul Birkel
 

Something like https://www.ebay.com/itm/Black-Box-CL410-Current-Loop-Interface-Module-powered-EIA-RS-232-20mA-101-4Q-Nos/111886999189 should do the job, but the BIN price is, in my opinion, much too high.  Even with free shipping.

 

From: VintHPcom@groups.io [mailto:VintHPcom@groups.io] On Behalf Of Martin Hepperle
Sent: Tuesday, October 15, 2019 5:38 AM
To: VintHPcom@groups.io
Subject: Re: [VintHPcom] HP 3081a ASCII terminals help

 

Richard,

three years ago I obtained two of these, brand new, but with the simpler numeric keyboard (no alpha keys). No barcode wand, but a magnetic card reader.
I liked the 1970s brown/yellow/orange color scheme and the VFD display.

The current loop interface uses a 3-wire setup, so not all TTL-current loop converters may work because the input- output loops share a common line.
HP sold an interface box for these units which i do not have.

For an electronics engineer it is probably easy to interface these to a RS232C interface, but I needed more help and found some interface schematics in an old BYTE magazine.
This simple interface consists of a transistor and an optocoupler plus a -12V converter.
I was able to send characters and escape sequence to the unit so that they show up on the display, but have not implemented the receiver part of the interface.
With the simple numeric keyboard it is relatively useless - with the alpha keyboard you could indeed use it to log into a system and even run a line editor session.

I can dig out the BYTE article in the evening at home if that helps

Martin

Join VintHPcom@groups.io to automatically receive all group messages.