Hi Guys,
Need a little help here ... 
I've seen in ultimarc's site that we can emulate emulation keys with the combination of two keys ... for instance, if we press "Player 1 Start" and "Player 1 Down" we have the key for "PAUSE GAME".
Question: If we connect one button to both keys in I-pac, do we have the same result when we press that button ?
Thanks,
Short answer - No!
Long answer - You would want to use diodes if you did this. Otherwise, whenever you pressed P1 Start, you would also press P1 Down (through the button contacts) and Pressing P1 Down alone would also Press P1 Start (and normally maybe Pause the game).
Even using diodes, this won't work with the I-PAC because of the way the Shift Key operates. Basically, pressing P1 Start and THEN pressing P1 Down activates the shift function in the I-PAC. Pressing them together does not (probably activates one or the other, but not both.)
I think you could do this without using the I-PAC's shift function, by say wiring a switch up with diodes to P2 Start and P1 Down, and then setting MAME up so that Pause = "2 and DownArrow". Or reprogramming the I-PAC so P1 Start was not the shift key and doing the same as above with P1 Start and P1 Down.
You can also do what you are suggesting with the KeyWiz (
www.groovygamegear.com) using Stealth-shifted buttons - see
http://www.fraggersxtreme.com/arcadepanels/encoder/shiftkeys.htm for a discussion of stealth-shifted inputs and
http://www.fraggersxtreme.com/arcadepanels/encoder/pausekey.htm for a discussion of wiring one button to two encoder inputs.