*4175 should do the job, but if you just push the alarm button and release it, that will silence that alarm and leave the trunk busied. JUST DON'T DIAL *31 or *32! That clears the alarm and the next time trunk 75 is accessed, alarm again. 'Constantly phantom calling and busying all the trunks in the system' is happening for a reason or reasons. Polarity problems, you reduced the number of lines without compensating in programming, or the phone lines are really 'in trouble'.

You need to get a qualified Mitel SX50 tech out there! I'm guessing this all started happening right after you changed your phone service provider, but they say there is nothing wrong with their equipment. Maybe, maybe not. Who hooked up the new lines and what were their qualifications.

Look at it this way. If someone dies, while trying unsuccessfully to dial 911 from a room at your property, because of 'lack of maintenance' on your Mitel SX50, who do you suppose is going to get sued? It won't be the phone company, unless a QUALIFIED Mitel tech determines that the problems you are having are because the phone company is providing lousy service, BEFORE somebody dies! A word to the wise!

When I was young, I was Liberal. As I aged and wised up, I became Conservative. Now that I'm old, I have settled on Curmudgeon.