A friend of mine is using 4-line phones for their business. There is no KSU. The phones just work off T/R. They would like to have Music on Hold on 3 lines. Ideas anyone?

Two guys at the local Radio Shack... Music on Hold? What's that? One actually said "We don't have that game."

WTF?

Some KSU-less telephones have an MOH input jack on the phones. Have you checked either the phones themselves, or the installation manual, to see if there are any?

Failing that, I would suggest a search for the phrase "moh ksu-less telephones" at our friends at Google. Here is one of several thousand hits:

MOH adapter for KSU-less telephones

At the bottom of the page is a device that provides what you want, albeit requiring an extra button-push each time, which might be a show-stopper.

EDIT MOVED: to Other Systems