Thanks for the response Harry,
My system is a Meridian 1.
I'm hooking a Telular Phonecell sx5e gsm fixed wireless terminal to an analog extension on the pbx. I can't get the "off-hook" light on the terminal to go out. The paperwork that came with the Telular terminal says: "The sx5e is able to detect both a pbx diconnect tone and an analog diconnect pulse. When a pbx detects a hang-up, the sx5e must be told to also release the line. This is typically done by either a disconnect pulse or disconnect tone, but is pbx specific". I can't fine this in the meridian 1 documentation.