The HP-IL (Hewlett-Packard Interface Loop), was a short-range interconnection bus or network introduced by Hewlett-Packard in the early 1980s. It enabled several devices such as printers, floppy disk drives, tape readers, etc. to be connected to programmable calculators such as the HP-41C, HP-71B and HP-75C/D, the 80-series and HP-110 computers, as well as generic ISA bus based PCs.

Read more about HP-IL:  Principles, Applications, How To Connect and Tips For 41 System, How To Insert The HP-IL : GPIB Converter Into The Loop

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Equipment With HP-IL Interface - Third-party
... FSI164A HP-IL/RS-232C Interface Leitz IL-41 Theodolite interface. ...