This read-only INTEGER (0 to 2147483648) is a monotonically increasing index assigned to each link currently configured to carry Cisco Switched voice traffic, where indexes are never reused even after a link is unconfigured for voice, and the counter wraps to zero and reuses a free value only once the maximum is reached. Administrators use this stable index to reference a specific voice-enabled link consistently across polls, even as other links are added or removed over time. For example, an admin building a long-term inventory of which links have carried voice traffic can rely on this index remaining a unique, non-reused reference for each link.