DIU Cartridge Bizarre Issue!

[ASTROMODAT]

Here's a question for you DIU Expert(s):

Regarding the encryption modules for the ASTRO DIU and the DIU3000...

In their respective service manuals, Motorola gives battery life expectancies for both the older style EMC cartridge that used a 9 volt battery, as well as the current UCM module that utilizes a 3 volt button cell. It states that the battery life expectancy (in both cases) is 5 years, IF the EMC/UMC covers remain closed. Otherwise, battery life drops to 3 years.

Why in the heck does opening the covers on the EMC/UMC cartridges vs/ keeping them closed affect battery life? And, I think (but I’m not sure!) that this is the case regardless if the EMC/UMC cartridge is, or is not, inserted into the DIU, or just lies on the shelf.

My only guess is that if one opens the cover on the EMC/UMC, the battery goes into effect (e.g., drags some small amount of current) because it has to retain key memory for a period of time before the tamper circuitry destroys the key memory? This way, if the cover remains closed at all times, you are just looking at pure shelf life, as there would be no current flow since there would be no tamper issue?

Larry