Section 18G. The statewide emergency telecommunications board shall require that each public safety answering point that possesses enhanced 911 service shall retain such tapes for a period of not less than six months; provided however, that said board shall require that if a public safety answering point utilizes a digital recording system, tapes shall be retained for a period of not less than one year; provided further, that the telephone companies shall be responsible for the costs associated with the purchase of additional recording media needed to fulfill the requirements of this section.