kwing, after reading this I don't think you can use the telsets on other older releases unless you can downgrade them??? the note in the warning below specifies that
2.4 Release 5.0 DCP Firmware
PLEASE READ AND UNDERSTAND PRIOR TO UPGRADE
This maintenance release includes updated firmware for the Avaya 2410/20 and 5410/20 digital terminals. When IP Office systems have been upgraded to 3.2(7) Q2 2007 maintenance release, the DS 2410/20 and 5410/20 terminals will automatically attempt to upgrade to this new release of R5.0 DCP firmware. Failure to have version R5.0 DCP firmware copied to the IP Office specified TFTP server will result in the terminals becoming non operational. Terminals will automatically restart after upgrading completes. When upgraded, the terminal can only be used on this maintenance, and subsequent IP Office maintenance and GA software releases moving forward. Remote upgrade of any IP Office unit needs to be fully aware of having the necessary R5.0 DCP files copied to appropriate TFTP servers prior to committing.
Note: - R5.0 DS terminals will request firmware upload if connected to 3.0 – 3.2 Pre-Q2, 2007 IP Office units. 2410 and 5410 requiring DCP 2.0 Firmware, 2420 and 5420 requiring 4.0 DCP Firmware. These builds are available on any previous 3.0 Admin CD.