This read-create Integer32 (131..510) identifies the LCN (Logical Channel Number)/PVC that this HDLC channel is associated with, applicable only to trunking applications where CCS frames travel over an AAL5 PVC (not applicable for PRI or GR-303, which backhaul CCS frames to the call agent instead). This lets an admin explicitly bind the signaling HDLC channel to a specific virtual circuit in trunking deployments, which is essential for the CCS frames to reach the correct destination over the ATM network. For example, in an AAL2 trunking setup, an admin would set vismHdlcLcnNum to the LCN of the PVC designated for carrying that line's CCS signaling frames.