The Hotel here has a mitel sx50. Sometimes when we try to call or set a wake-up call, the console says "LOCKED" for that room number.
Any help? Thanks.

James

'locked' means the room has been offhook too long with out dialing! Or, the system THINKS it's been off hook too long (shorted pair, bad phone, etc.)!

If it was locked out for a long time (and you are sure the phone is now back on hook) you may have to resort to resetting the system to clear the problem.