>>We have a HP Laserjet 3p attached to a medical device. The medical device is running a custom real-time operating system. The laserjet 3p is starting to die. Does anyone know how I can find out which printers (HP or not) are backwards compatible with the Laserjet 3P? Becuase of the OS, we can't install a driver for a new printer onto the medical device.
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>The HP site no longer seems to list IIIP specs. The best I could find was http://www.printerworks.com/Printers/LaserJet_IIP_IIIP.html
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>According to that, the IIIP supports PCL5. My understanding is that all HP PCL language versions are downwardly compatible, so any printer that supports PCL5 or higher should be compatible. The printer will need to have the same interface currently used by the IIIP (parallel or serial).

Thanks Al. I will pursue this.

>NOTE: the printer must NOT be a so-called GDI printer ( FAQ#15418 ). It needs to have an on-board processor and RAM. In some cases the only way you can tell if a printer is non-GDI is to see if it supports DOS and/or Linux (i.e. something other than Windows).

We had a few GDI printers, what a pain in the neck.

>Of course, the first place to ask in this case is with the manufacturer of the medical device. With a non-Windows OS, it's possible they are doing something such as querying the printer to make sure it's what the device expects. Manufacturers like that really like to control their hardware environment; even if you find/install a compatible printer, you may find that doing so voids the device's warranty.

In this case the device is way out of warranty and is no longer supported by the company, so we are stuck trying to keep it running until funding can be found to replace it. Good point though, lots of testing will need to be done.