Electrical – Pin letters not shown in circular connectors D38999 series

connector

I'm working with military circular connectors of the D38999 series and I've discovered that when the connectors have their pins designated by letters instead of numbers, some letters are not shown.

For example, in this image, the letter "O" is not shown:

enter image description here

I've done about 10 different Google searches and I can't find any information on this. Does anyone know which letters are not shown (both capital and non capital)? If anyone has some site/pdf file about this it would be great too.

Also, somewhat related, is there a part in Orcad that is a connector that has pin names in letters and not numbers?

Thank you!

Best Answer

The pin arrangements for 38999 connectors are specified in MIL-STD-1560 (link is for MIL-STD-1560C).

enter image description here

'I' and 'O' are omitted for obvious reasons

Here is another example with some lower case letters omitted as well as 'Q':

enter image description here

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