An unusual package of telecommunications and office computer systems services is being offered to current and prospective tenants of two new office buildings in Arlington.

Instead of buying telephone and word- and data-processing equipment, a would-be tenant can lease such equipment on a month-to-month basis or for a longer period along with the building space itself. Other offerings include access to such services as high-speed copying, telexes, a message center, word processing and even temporary help.

The advanced tenant services, being offered by Building Systems Co., a subsidiary of United Technologies Corp., are now available in Charles E. Smith Cos.' Crystal Gateway II and will be available in Crystal Gateway III, which is under construction and scheduled to open next January.

United Technologies' "response center" in Crystal Gateway II is used to demonstrate what is available to tenants. For instance, the receptionist uses a UTC Lexar telephone console to answer the phones. When the phone rings, the digital display area tells her from what phone number the call has been made, what time it is and the number of calls waiting to be processed.

The phone system sends outgoing long-distance calls through the least costly routing and provides detailed itemized bills (extension, number called, time spent on phone). It allows a caller to be talking to, say, Seattle while computer data are being transmitted through the same phone to another city. Another feature provides up to five lines using the same number for a substantial savings. It also allows a person to dial numbers without lifting the receiver so other tasks can be continued until the party answers the call.

If the person calling in wants to talk with someone who is out, the receptionist types a message into the adjacent computer, to be called up on the screen when the person returns to the office and checks in--something done by computer.

The computer system in the Building Systems Co. office is programmed so that the "message center" is displayed first when a person signs on, then the "in basket" of correspondence. A person's daily schedule can also be displayed.

"There is no paper generated in this office," says Thomas W. Colligan, regional manager for BSC's Washington operations. The drawers in the office's file cabinets are filled only with computer programming books and equipment. Colligan also mentioned that he has programmed 180 reminders to himself that will pop up on his screen on the right day over the next three years.

Building Systems Co. has retrofitted the 14-story Crystal Gateway II building to provide a "data highway" through the core of the building. The data highway--a fiber optic communications network--allows the interconnection of all segments of the automated office. By using the plugs throughout the offices, tenants can hook into the network and obtain a wide variety of electronic office tools, including the data terminal, personal computer, display writer and telephone.

"We try to create an enhanced building which is differentiated from the rest of the world," says Edgar O. Cheney Jr., BSC vice president of building services. However, Cheney points out that a tenant does not have to buy or lease any of the services when moving into the building.

"We're telling them, 'you don't have to invest in all this equipment; we have made this investment and we'll share it with you,' " Cheney said. "We're trying to promote effective utilization of technology."

In addition to the equipment available for individual offices and the training that accompanies it, tenants may subscribe to BSC's computerized office services, which can provide them with access to some sophisticated automated equipment many don't have the capital to invest in individually, he noted. In addition, by sharing a large computer and other expensive equipment with a lot of tenants, smaller firms can reap the benefits of lower unit costs.

The arrangement also frees the tenant from the task of trying to become an expert in the ever-expanding range of advanced automated office equipment. "Lawyers shouldn't have to run copy centers, but they don't have the opportunity not to," he said. Another benefit: "We stay with the equipment, we own it, we run it, we maintain it." Moreover, Colligan said BSC isn't wedded to any particular manufacturer but has a shopping list of equipment available.

With the overbuilding in the local office market, Colligan contends, BSC's tenant services add something new to the competition. "One hundred companies could sell you a phone, word processing, data communications," he said. "We're trying to provide one-stop shopping."

Another device being demonstrated in BSC's response center automatically turns lights on and off. Called Infracon, the small sensor on the ceiling senses motion in the room to turn the lights on. Lights then go off after 15 minutes if there is no movement in the room. The device also can be used to control heat or as a security sensor hooked into a computer, Colligan noted.

Infracon is not available as part of the tenant-services package.

BSC is playing a larger role in Crystal Gateway III than Crystal Gateway II. In addition to offering business communications systems, it is also coordinating the system design and installation of elevators, ventilation and air conditioning and will provide ongoing computer-based electronic energy management and temperature control of the building when it is finished.

United Technologies' entry into the electronic building-management field is an extension of its work in developing electronic environmental-control systems for aircraft and spacecraft, UTC officials said. UTC's Building Systems Group includes Otis Elevator Co., the world's largest manufacturer of elevators and escalators; Carrier Air Conditioning, the largest manufacturer of air-conditioning, heat and refrigeration equipment, and Lexar Corp., a manufacturer of telephone and data transmission equipment.

The conglomerate has been systematically building up its building-management equipment and services group. Last year, it acquired General Dynamics Communications Co., which has the largest non-Bell installed base of PBX telephone lines in the country, and the private-switch business of Stromberg-Carlson Corp. Last month, it added to its office services capability by acquiring the privately-held Headquarters Companies Inc. of San Francisco. The firm provides advanced office services on a "pay-as-you-use" basis through a network of 50 centers in major buildings across the country, including an outlet in the Washington area.

United Technologies is in the process of finishing work on the 38-story CityPlace office tower in Hartford, Conn., which is being billed as "the world's first intelligent building." When it opens in September, the building will have its own computer "brain" to monitor and control the elevators, heat and ventilation, air conditioning, lighting and energy use and security and fire systems. The company also will offer tenants its telecommunications and office automation systems.

United Technologies has been involved in several other major building projects; its energy management system has been installed in 34 buildings at Massachusetts Institute of Technology and at Walt Disney's Epcot Center at Disney World, and it is working on the LTV Tower in Dallas.