We have a lot of analog extensions that can be accidentally left off hook for long periods. They are on VG350 gateways setup as SCCP to CUCM 10.5. When they are off hook, they have dialtone, followed by a call cannot be completed as dialed message, 2...
Do the 8800 series (8811, 8841, 8861) phones support Idle Display, and are the specifications documented? The manuals seem to indicate yes, but points to an article that is very old and doesn't seem like it should apply to new color LCD phones.
That definitely isn't how it is working on VG310 (which doesn't use MGCP, they are all SCCP). The device pool SRST reference does not control SRST at all.
Now that link is broken. Is there a replacement for the document online somewhere, it is still referenced all over Cisco's documentation for AQM and other current products.