Hewlett-Packard Interface Loop
![](https://upload.wikimedia.org/wikipedia/commons/thumb/e/e7/0975_6_7_-_HP41_Interface_Loop.jpg/220px-0975_6_7_-_HP41_Interface_Loop.jpg)
Hewlett-Packard Interface Loop ( HP-IL ) is a bus system developed by Hewlett-Packard in the early 1980s or a simple network technology with a defined interface for connecting in-house pocket calculators and microcomputers with e.g. B. Peripherals. Initially designed for the programmable HP-41C , HP-IL was later used in the HP-71B and HP-75 . The necessary driver software was either already in the computer or on a corresponding expansion module that also contained the hardware of the interface. Numerous devices have been developed by HP and other manufacturers for HP-IL, including thermal and inkjet printers , cassette drives , measuring devices, video outputs, etc.
The HP digital cassette drive (HP 82161A) was particularly popular because it was battery-powered and cassettes that corresponded to those of dictation machines could be accessed in the same way as floppy disks or hard drives (i.e. fully automatically controlled). In this way it was possible to work completely autonomously and still (for the conditions at the time) to save very large amounts of data. Programs could also be loaded dynamically.
HP-IL used a current loop that connected all devices together and ended again at the output computer. They expanded simple pocket calculators into full-fledged computer systems and can be seen as an early forerunner of USB .
Devices with the HP-IL interface (selection)
Controller
- HP 82160A - HP-IL module for the HP-41C
- HP 82973A - HP-IL interface for IBM PC and compatible with ISA bus
- HP 82938A Interface for Series 80 Desktop Computer / Controller
- HP 82401A - HP-IL module for HP-71B
- HP-75C / D
- HP-71B
- HP-110
- HP-150
Interfaces
- HP 82164A - HP-IL- / RS-232C interface (serial)
- HP 82165A - HP-IL / GPIO interface (generic parallel output )
- HP 82166A - HP-IL converter (smaller version of the GPIO interface for embedded applications)
- HP 82166C - HP-IL Converter Prototyping Kit
- HP 82169A - HP-IL / HPIB interface (bidirectional)
- HP 82985A - HP-IL / NTSC video (monochrome)
Periphery
- HP 9114A / B - floppy disk drive
- HP 82161A cassette drive
- HP 82162A - Thermal printer (HP-IL version of the HP 82143A printer for the HP-41C)
- HP 82163A - Video Interface
- HP 92198A - 80-line video interface (Mountain Computer)
- HP 82168A, 92205M - acoustic couplers (modems)
- HP 82905A / B printer
- HP 2225B - ThinkJet Printer
- HP 7470A - Graphic plotter (Opt. 003 HPIL interface)
- HP 2671A / G - Alphanumeric, graphic thermal printer
Test instruments
- - HP 1630, HP1631 logic analyzers (Can be loop controller)
- HP 3421A - Data Acquisition / Control Unit
- HP 3468A / B - Digital Multimeter (HP-IL version of the HP 3478A with GPIB)
- HP 5384A and HP 5385A - Frequency counter, with option 003 (HP-IL)
software
- HP-IL developer module (plug-in application ROM module for HP-41C)
- HP 82183A - Advanced I / O module
Third party manufacturer
- FSI164A - HP-IL / RS-232C interface
- Leitz IL-41 - theodolite interface