When meters are used in connection with telephone service, the meter reading records from which the customers' bills are prepared shall show: Identifying number or means to determine readily the customer's name and service classification; Meter readings; Date of meter reading. As nearly as practicable, meters shall be read at monthly intervals. When mechanical or electronic means, or both, are used for recording information that will affect a customer's bill for local or toll service, or both, the equipment shall be inspected after installation and periodically tested in order to insure its proper functioning and accuracy. The utility shall keep records of malfunctions. The retention period for these records shall be 1 year. Public Utilities Article, §§2-121 and 5-101, Annotated Code of Maryland Effective date: January 1, 1976 (Order No. 61496)