Call collisions as such cannot occur at the network. Any simultaneous incoming or outgoing calls are dealt with separately and assigned different call references.
Channel selection conflicts may occur if an incoming call and outgoing call select the same channel. This is resolved by the network through channel selection mechanisms described in 5.1.2 and 5.2.2.
In the case of such conflicts, the network shall give priority to the incoming call over the call request received from the user. It shall clear the outgoing call whenever the B-channel cannot be allocated by the network or accepted by the user originating the call.
Note - Some terminal adaptors supporting existing non-voice terminals (e.g. Recommendation X.21) may need to resolve double channel selection by clearing the incoming call and re-attempting the outgoing call setup in order to satisfy the requirements of the interface at reference point R.