This read-only INTEGER selects the echo canceler's idle-code pattern, with different meanings for mu-law (7f, ff, 7f-or-ff, or f7) versus a-law (none, 54, 55, or a programmable idle code) encoding, defaulting to pattern3 for mu-law and pattern2 for a-law. This tells the echo canceler what bit pattern represents an idle/unused channel for the line's encoding law, which matters for the canceler to correctly distinguish idle channels from active ones. For example, on an a-law E1 line, an admin would expect vismEcanCnfIdlePattern to reflect pattern2 (the 0x54 idle code) by default rather than a mu-law-specific pattern.