I see where the 508 says it has a line input for "Music on Hold", however can someone tell me if the "Hold" button on a standard phone set actually conveys any message at all to the ATA? I know if you press the Flash button that the Obi detects it and does what ever. But doesn't the Hold button simply mute the microphone and allow the user to hang up? I didn't think the ATA was ever aware that hold was pressed. I asumed the hold button would only really be valid with SIP phones...?