Hi Bundy33,
This may be way off the mark, but was a problem that I had with phantom calls to night extensions. The calls were happening at the local site and their head office. The calls were being presented to the night extensions, and the "on-call" staff.
Why did the calls only go to those staff? Because they were the only people that had their phones turned on in the middle of the night. The calls probably went to many other unanswered (unmanned) phones.
The reason you can't trace the call is that it has terminated faster than you can hit the MCT button. Basically just after the call was placed.
I gave the staff a hammering with all sorts of questions to find out when, where, why, etc, and who was getting the calls and at what times and what they heard (usually dial tone, but sometimes an "open but scratchy line" then dial tone.)
After many many hours of searching phone bills and numbers and clues, the common item to all of the problems was that all of the phone numbers getting phantom calls were listed in the local offices Abbreviated Dial list.
The customers speed dial list had the night switch positions stored under short numbers like 1111 or 1121 etc.
Their head office also had their directory number listed in our local offices Abrev Dial list with a similar string of numbers. The abbreviated dial Access Code was 1(one).
A few clues to what can cause this fault are,... the system must have analogue extensions, and pulse dialing must be operational on the PABX, but not necessarily set to pulse on the telephone set itself. Something must be "shorting" one of the extension lines. Also another interesting thing that has just come to mind is... The system has least cost routing, and I would bet on the number being stored and forwarded, rather than the call progressing digit by digit.
The cause of the problem was a cable fault at the site (or just one faulty phone) that was dialling ones and two's very easily with short pulses. The call would be placed. The call would drop out.
Now the question is, how do you find which analogue circuit is causing the problem?
Maybe you could set the destination to an internal extension that is manned at night that has a display phone attached, or log unanswered calls on your call accounting system or disable decadic dialling on analogue extension circuits, making sure that all extensions can dial with DTMF dialling.
And just to put a spanner in the works, the PABX that I had this fault on, was not an MD110, but it doesn't really matter, because the fault you describe is not system specific to an MD110 and may not even be at the site that is receiving the calls.
Regards, Munz.