Within the last three weeks, we have developed a hum on our land land that remains after dailing and during all calls on our land line. I checked at the d-marc and there is no hum, so I conclude it to be an inside wire problem. We use portables in the house(have for several years.) Unpluged all prtables an d used a standard corded phone to check several jacks, and have the hum at all. The inside wire was installed when the house was built in 1998, and the problem has nerver occurred before. Is there a way to check jacks to find out if one of them has developed a loose connection?(Without removing the coverplates and reconnecting contacts) Is this something that can be addressed by a professional repairman more efficiently than diy?

Short of acquiring a Transmission Impairement test set and learning how to use it. Taking the cover plates off and checking is the easiest.

EDIT: Many times the jacks are daisy-chained in homes, and one loose connection can cause the problem on all successive jacks.

Tough one. Not necessarily. Best way is to plug all the phones back in and verify that you still have the hum. It's entirely possible that it might have went away by reseating the contacts.

This is difficult because you either have to inspect or disconnect at least one wire.

At home, I have a screw type demark spot because of old quad wiring. It's relatively easy to pull a wire off.

The demark outside is another place to try to disconnect. Sometimes all the phones terminate there.

Really don't know what you have and phones can also be daisey chained + home runs like in my house so it can be a real mess.

It can also be individual cables.

Suspect jacks and CABLES that could have gotten wet. Cobwebs in the jacks are another possibility.

If 1 of the conductor is touching ground it will hum, drill any holes lately?
You might be able to use a different pair(yellow and black instead of red and green).