High Telephone line noise with missing door opening via “DTMF” issues and causing terrible audibility from the visitor to the tenant?

• Tip and Ring Bi-directional signalling is not differential or in-ground current noise issue:
  • Install a 0.1 Micro farad capacitor in series to the Tip. Then line test:
    • If the signal/noise improves then Line is unbalance. Request Line Card change-out; OR
  • Disconnect Tip and Ring from the module. Measure the voltage ( potential) between Tip and Chassis ground. If voltage exceeds 2.0-2.5 volts:
    • then run a 10AWG/Stranded cable from the telephone access unit to the communication demarcation point to ensure voltage drops to approximately 0 potential difference; OR

Change out the power supply. Ensure the power supply ground is connected to the power ground and not the communication ground.