Hello - 

     On most switchers, there is a difference between the Key On/Off state and the tally.  The keyer ON button will light up to let you know that the keyer is active.  However, just because it is active does not mean that it is contributing to the on-air signal.  As John said, a keyer can be turned ON, but if it is going through a 2D or 3D DPM, it may be off-screen; it may be rotated to edge-on; it may be cropped; or its opacity could be down to 0% - in each of these cases, the keyer is contributing as part of the on-air signal, and it will not show a tally.  If you change the opacity from 0% to 1% you will see the tally come on - or if the circuitry detects that the key has been slid on to the active picture or if the crops are enlarged to where you can actually see even a small part of the key...then you will see a tally.  But in the same way that if you turn on a keyer on an M/E and do not put that M/E to air you will not see a tally, so too is it when the keyer is moved off-screen with a DPM.

The DPM tally rules are that if there is no key signal on screen then there is no tally so what you said first seemed right. It should be the same rule no matter wihich keyer is using a DPM and whichever ME you work on. I would make sure by using SHOW KEY that the DPM has tzken all the key signal off screen when you see the problem. Do 2D DPMs as well as iDPM do this? Which version of software are you using?

John