S.C. Code Regs. 103-663.2. Equipment Requirements

A. The central office and interoffice trunk equipment shall be maintained so as to meet the following standards during an average business day (8:00 AM to 5:00 PM): Failure rate on intraoffice calls— <1.5% Failure rate on interoffice calls— <3% The failure rate for interoffice calls applies to EAS and multioffice trunking calls but not to toll calls. B. The central office and interoffice trunk standards are the objectives to be used by the ORS staff when testing. The telephone utilities are not required to perform tests or maintain records of these items.