The software in the 390x sets is depending on the software in the pbx.
If you buy a phone with rel 3 and the pbx cant support such a high software release it can be necessary to "down-grade" the phones to make them work.
If you have phones with to low software level you cant use all features in the phone/pbx.
If you access LD 32 in your pbx you can type the fsum command.
**M3904 SUMMARY
046 - ON DISK This is the software level for the M3904's
052 (017 ) - 000001 SETS FOUND
041 (017 ) - 000004 SETS FOUND
046 (024 ) - 000017 SETS FOUND
This is a list of what software your pbx has and what software your phones has.
you can then update the software in the phones by doing a download from the pbx. This can be done to one or all phones at a time. However, to make it to all phones at once is nothing one should do during daytime. It takes a long time, depending on the amount of phones that should be updated.
You can manualy update one phone at a time by typing this commands: (takes about 10 minutes each)
Options
FDLF l s c u - Forced download to one unit regardless of state or current version.
FDLI l s c u - Conditional download to one unit regardless of state or version.
FDLU l s c u - Conditional download to one unit.
l,s,c,u is loop,shelf,card and unit number. (TN)