HP-41C Video interface PAL/NTSC?


I would like to buy a HP-IL video interface module, but it is not clear to me if it will support PAL standard.
Any clue?


Giuseppe Marullo


The HP one (82163A) comes in either PAL or NTSC.

The Mountain Computer inc (80 column) (MC00701A, alias HP92198) allows the user to select the video format.



Hi Vassilis,
thank you for your answer. I don't have the module, I should ask the seller to check.
Since he is in the States, I guess it will be NTSC, any hint on how to check it other than testing it?
He does not have a 41C at the moment.

It could be used thru the monitor port anyway? What kind of monitor signal is?

Thanks again,

Giuseppe Marullo


Hi Giuseppe,

I don't think you must care about this. As for early 80's TV sets were designed to handle one specific system PAL, SECAM, NTSC... but remember those are colour modulation system, so the colour information in the composite video signal becomes useless from one system to the others. But colour is not an issue with HP-41 system, as they only offer B&W.

Next thing to care is luminance (the real B&W image), and again, nothing to care about, signals are compatible at this level.

Synchronism is the last point, PAL uses 625 interlaced horizontal lines and 50Hz vertical refresh rate, while NTSC handles 525 interlaced lines and 60Hz vertical refresh... This sound quite different, but they aren't. In fact almost every TV set manufactured since early 90's handles both systems efficiently.

So you can symply plug it into your TV set video input (usually an RCA type coaxial connector) or to the V-IN line if you are going to use an Euroconnector (Scart).

The signal itself is a composite 1Volt peak to peak assymetric video. Video info goes from 0 to +0.7v while sync pulses go from 0 to -0.3v.

Anyhow, you must be carefull if you are intended to use an old B&W monitor, as those are usually suitable for one specific video system.

Hope this help


Dear Giuseppe,

as Diego explaines in his answer, the IL-video interface box generates an FBAS signal. This is compatible to valve-monitors.

If you interface the FBAS singnal to an modern LCD screen you get an incomplete screen display, because the line format of LCD monitors is different from the line format of valve-monitors. That is terrible because a small LCD screen (used for automotive applications) would be a nice extension for your IL-system...

Alternatively to the IL-Video interface box you are able to use your PC-monitor as screen display. For example the software soultions TRANS41 and EMU41 includes a screen display feature. Furthermore this solution (I prefer EMU41) gives you much more advanced features, much more than a poor screen dispay output. Refer to the articles forum item 311 : "HP41-PC gateway & emulator"...

Best wishes from Germany - Christoph Klug


Just for the record:

"FBAS" is a German acronym (Farbsignal,Bildinhalt,Austastung,
Synchronisation"), the internationally better known term is
CVBS (color,video,burst,sync).



An appreciated and much needed clarification, thank you!


Thanks for your answers. I will purchase them, if I have understood well the signal is 1Vpp composite, so any frontal RCA / SCART connector will let me see the images.

Christoph, are you saying that a HP-IL LCD module would sell well? :)

Giuseppe Marullo


Dear Giuseppe,

LCD monitors I tested are not able to display any line of the IL Video Interface correctly - form this result incomplete characters. That is bad, because the LCD´s have a small size, which is pratical for a portable system :-(

Personally I prefer EMU41, this includes also an Video Interface screen output running inside a DOS window...

Best wishes from Germany - Christoph Klug


So I only have to interface a LCD display (like a 128x64) to a HP-IL bus, right?
Wow, another project.


BTW: There exist at least two versions of LC displays from CMT for HP-IL...

Since these are relatively rare, it would be nice if someone will be able to develop a new solution.



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