The General Services Administration is planning to seek competitive bids for a new federal telecommunications system in the Washington area that would include state-of-the-art technology allowing telephone lines to carry computer transmissions, monitor room temperatures and in special cases allow two-way video communications.

While the dimensions of the system in a given federal office will be determined on a case-by-case basis jointly by GSA's Office of Information Resources Management and agency managers, GSA officials say the new program means that the Chesapeake & Potomac Telephone Co. -- now part of the Bell System -- will likely lose its monopoly on government service. eregulation of the telecommunications industry over the past several years has made the bid process on telephone services and equipment purchases advantageous. For seven years, GSA has sought competitive bids on similar telecommunications service contracts for federal agencies operating thorughout the country. In 38 instances, Bell System affiliates have won those contracts -- sometimes because no one else bid -- while in 23 other cases, small firms have won the contracts.

For example, Centel has installed 3,500 telephone lines previously provided by Bell in Houston, and is installing a 7,300 line system for Denver federal offices. In Las Vegas, 500 government lines are managed by Las Vegas Communications, Inc., and in Fort Lauderdale, Fla., 250 government lines are run by First Communications Corp.

"Now that there is competition in the marketplace, we have a greater opportunity to reduce costs to taxpayers and keep costs under control," said GSA's commissioner of the Office of Information Resources Management, Frank J. Carr. His view was echoed by Bell competitors.

Robert L. O'Brien, vice president for government marketing for Northern Telecom, Inc., said the government's "current system is overburdened and obsolete as far as features are concerned. They're currently receiving service from Bell and it was not really designed to their operations as they are today."

O'Brien said competitive bidding on equipment will "allow both updating technology and offering cost savings throrough ownership or lease programs."

"We have the feeling that there is a strong possibility of saving (the federal government) a great deal of money," said T. Mark Benjamin, federal government sales manager of the Rolm Corp., a major telecommunications systems manufacturer. "Historically, it has been shown that there can be a cost avoidance of 30 to 50 percent by going outside the Bell System."

"Sure, C&P is going to lose its monopoly," said Carr. "And it will likely lose millions of dollars--unless they have the low bid all the way."

Carr's plans are guided by a 44-page report by a GSA advisory panel, the Washington Telecommunications Interagency Committee. Their June study said federal telephone service in Washington is too costly, unmanageable, non-competitive, outdated, inflexible and inadequate for all but basic service. he panel recommended installing a system that can handle not only voice, but also "integrated office automation transmissions" such as computer terminals and word processors. It also said the system should be able to handle some relatively futuristic devices, including:

* Teleconferencing, where many people in different locations can connect to the same line.

* Sensor services, that can monitor heating and cooling, for example.

* Security, that can detect people in rooms during off hours.

* Video hookups, which could have one-way or two-way face-to-face communications involving television-like cameras.

"We want to be able to send a letter, a communication if you will, from one executive to a subordinate without creating a lot of paperwork," Carr said. The system would work much like the controversial proposal that is endangering some of the U.S. Postal Service's business -- electronic mail. But it would be within the govenrment's complex.

The multi-million dollar system is likely to be created in stages, with the first funded in the fiscal 1984 budget cycle, GSA said. Overall, in the metropolitan area, there are 610 separate government-owned and leased office buildings with more than 250,000 telephones served by C&P.

The first agency affected will be the State Department, which said it had a pressing need to procees communications from its embassies and counsulates abroad and can't wait.