After the Montgomery County Council ratified the cable television contract with Tribune-United of Montgomery County last week, a cable official remarked offhandedly, "Now our work really begins."

The work, at least for this stage, is the construction of the system, which at $130 million to build is one of the most costly cable systems in the nation and potentially one of the most lucrative.

"Building the system is a mammoth task," said firm spokeswoman Fern Krauss, involving complicated contracts, subcontracts and deliveries.

The firm has hired a new general manager, John T. Schmuhl from Warner Amex QUBE in Columbus, Ohio, to oversee construction.

As soon as the first homes are close to being wired, the work also will include a countywide advertising campaign to let potential subscribers know what the system has to offer and how they can sign up. The advertising is almost as important as the construction, cable officials have said, because the public must be sold on cable before it can be hooked up.

That campaign for subscribers will consist of newspaper advertisements, door-to-door sales and press announcements.

"You'd have to dig a hole six feet deep and cover it with dirt to miss us," Krauss said. "As we go along the streets, people will know we're coming. Once the wire is laid, the service will follow right behind."

Representatives of the firm will appear before the Montgomery County Planning Board to seek special exemptions from the county's strict zoning laws: Tribune-United will need to find homes for its huge receiver discs and for its community-access centers around the county.

More than 2,000 miles of cable will connect residential homes and apartments via cable wires strung from utility poles or, in some cases, run underground. A separate cable network will connect businesses, schools, government offices, libraries and other nonresidential institutions.

The cable wires will eventually cross more than 217,000 homes, meaning many subscribers will be able to sign up for and receive one of the three tiers of cable service starting with 42 channels at $1.50 a month. Based on the results from other jurisdictions with cable, about half of those 217,000 homes can be expected to sign up initially.

Cable firm subscribers will need to have their television sets fitted with a special $15 hook-up to accommodate all the new channels. That installation fee will be waved for the first few months. Various tiers of cable service will offer satellite television (to be competitive with independent television companies), Cable News Network, Spanish International Network, weather and options for movies.

One of the more innovative features of the system will be two-way communications that will allow the viewer to "talk back" to the television set. This will eventually be used for a variety of two-way interactive services, ranging from banking to grocery shopping to taking Spanish lessons via the living room television screen.

As part of its contract with the county, the cable firm also will offer public access channels.