Customer  is asking for a way to keep a telephone line engaged until a line drop signal is actuallysent. So that a panel can release a talk/listen key without actually get theline dropped, useful as the engaged line is shared across multiple users.
Answer: This all depends on who made the call originally 
If the intercom panel made the call then the simple test way would be to make a route from a spare portto the TEL-14 , or place the TEL-14 into a conference with a spare port  As long as there is a route made to the Tel-14 line the line will stay up
If a remote caller made the call then 
The option “Disconnect by Remote Hangup only” is what you want to enable on theTEL-14. That way the hybrid won’t release the line unless the remote end hasterminated the call or you have send the “Line Release” signal from a panel.