Bad Checksums and Line Noise

Symptoms

Data shows 'B' (bad) instead of 'G' (good) checksum. Caller ID data may be garbled or missing digits.

Causes and Solutions

• DSL interference — Install DSL filters on all devices sharing the line
• Long cable runs — Move device closer to demarc point
• Multiple devices — Remove splitters, fax machines, and other devices from the line
• Poor wiring — Check for corroded connections, replace damaged cables
• Low ring voltage — PBX extensions may not provide standard ~90V ring voltage

Diagnostic Steps

1. Connect device directly at demarc with no other equipment
2. If checksums improve, add devices back one at a time to identify the noise source
3. Contact telco if noise persists at the demarc — the issue may be in the outside plant