ths procedure is iniciated when the called is a fixed analogic number and hook the call. The remote switch must send a Suspend msg in order to suspend the call. The the called number can reactivate the call and the remote switch must send a Resume message. In your swicths you must have a SUSPEND/RESUME timer (I,dont know witch TXXX ) usually 90 s in order to release the call if you dont receive RESUME msg (sometimes its happens) , cause you could have “infinite” call if Calling Number doesn,t release the call
One a subsciber B Hung UP, the MSC will send Suspend message instead Release, when sending SUSPEND the circuits will be mainted, when the MSC will whait until the Timer T6 expire in order to release the circuits, but if the user Pick Up again before T6 expire, the MSC will send resume message to continue the converstaion.
Looking back to my ISDN – Integrated Services Digital Network – days.
ISDN was based on Q.931 (signalling) and introduced the notion of
2B+D for the Wireline local loop and 30B+D (Primary Rate Access (PRA)).
D channel was for signalling and the B channel was the “bearer”.
I.420 ws used for 2B+D, I.421 for I.421 (PRA)
Suspend/Resume is an ISDN service that allows calls to be “suspended” and “resumed”
Therefore, ISDN calls can be “suspended” (put on hold) to allow another call to use the B channel.
ISDN suspend/resume messages manage suspended calls.
For ISDN, ISUP (ISDN User Part) was meant to be the signalling protocol to be used.