Hi Geoffrey,
Here is some DLU/CCM info;
The Cisco CallManager server where the license file is loaded, assumes the functionality of a license manager.
The license manager serves as the logical component that keeps track of the licenses that the customer purchases and the licenses that customer uses. It refers to the processes that control the checkin and checkout of the licenses. It keeps track of the number of license units that are required for each phone type. The license manager has responsibility for issuing and reclaiming licenses, and detecting whether there is an overdraft of licenses.
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide_chapter09186a0080531ebb.html#wp49438
Device licenses are required for Cisco devices and for third-party devices, with the flexibility to replace third-party devices with Cisco devices. Device licenses are sold in increments of device-license units (DLU's). Device-license units are assigned to each device connected to Cisco Unified CallManager 5.0. Each device is assigned a unit number based on the type and capabilities of the device. Devices with more complex and high-end capabilities are assigned a higher number of units compared to devices with basic capabilities,
Here is the DLU breakdown;
Cisco Unified IP Phone 7902G = 1
Cisco Unified IP Phone 7905G = 2
Cisco Unified IP Phone 7911G = 3
Cisco Unified IP Phone 7912G = 3
Cisco Unified Wireless IP Phone 7920 (no battery) = 4
Cisco Unified IP Conference Station 7936 = 3
Cisco Unified IP Phone 7940G = 4
Cisco Unified IP Phone 7941G = 4
Cisco Unified IP Phone 7941G-GE = 4
Cisco Unified IP Phone 7960G = 4
Cisco Unified IP Phone 7961G = 4
Cisco Unified IP Phone 7961G-GE = 4
Cisco Unified IP Phone 7970G = 5
Cisco Unified IP Phone 7971G = 5
Cisco Unified IP Phone 7985G = 6
Third-party SIP device (basic) = 3 (third-party)
Third-party SIP device (advanced) = 6 (third-party
From this doc;
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_qanda_item0900aecd805009fc.shtml
Here is another excellent doc;
http://www.cisco.com/warp/public/765/tools/quickreference/ipphones.pdf
Hope this helps!
Rob