In the 1970s digital technology was introduced into the core of the public switched network. Relying on computers, digital switching routes both voice and data through the switch in the form of 0 or 1 binary coded information. Switches are the hubs of the public network; access lines carry traffic to and from subscribers. Telecommunications companies are, under law, subject to government oversight to ensure a high quality of service and reasonable charges to subscribers. This regulation is exercised at the federal level by the Federal Communications Commission (FCC) and at the state level by public utility commissions (PUC) or public service commissions (PSC). The private enterprise approach requires in the design of rate structures a balancing of the public interest with the interests of the investors in the venture. Local exchange rates generally are established on a statewide basis. Until the 1970s there was essentially no competition for local or long-distance telephone carriers.