Every public agency or public safety agency within its respective jurisdiction may establish a basic or sophisticated system. The establishment of such systems shall be centralized where feasible. Any system established pursuant to the Oklahoma Emergency Telephone Act may include a segment of the territory of a public agency. All systems shall be designed to meet the requirements of each community and public agency served by the system. Every system, whether basic or sophisticated, may be designed to have the capability of utilizing at least three of the four methods specified in paragraphs 3, 8, 9 and 11 of Section 2802 of this title, in response to emergency calls. In addition to the number “9-1-1”, a public agency or public safety agency may maintain a separate secondary backup number, and shall maintain a separate number for nonemergency telephone calls.