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 deal breaker.


Arthur P. Bloom
"30 years of faithful service...15 years on hold"