The lead could be for use with a printer if there are only data signals for one direction only.
I have lots of 4-pin DIN leads. But that's because about 30 years ago I invented my own "standard" that uses them as power connectors for +5V and +12V power leads. The reason for using 4-pin DIN connectors was because very little equipment appeared to use them
Mark
Standby alert
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer in Somerset later in the year
QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
Standby alert 