Brussels — Watching television in Belgium is like sitting in on an uninspired debate at the United Nations. Viewers can take their pick from programs on 16 channels beamed in by cable from 6 countries speaking 7 languages.
The country is easily the world's most heavily cabled nation, with nearly 90 percent of the 3 million TV owners wired up and working. While the rest of Western Europe still lags behind, serious efforts to catch up have begun from Italy to Sweden, from the United Kingdom to West Germany.
Yet few rules governing this new ''trade'' in verbal and visual communication have been laid down by national or international authorities, leaving program producers in one country relatively free to feed whatever they wish to any other country, provided the technical means for doing so exist. Common sense has been the law - until now.
Under pressure from governments and consumer organizations, some earnest head-scratching and soul-searching have begun among policymakers in the field, and so far they have focused their attention on what in the end could be the trickiest issue to face up to - advertising, and how much and what kind.
The business community has argued that to place too many restrictions on the volume and content of television advertising would be to tread on that cherished democratic ideal - freedom of expression. For its part, the consumer movement has said that the public must at the same time be protected from ''harmful'' influences.
Resolving the issue could take years, and there is little hope that it will be dealt with to everyone's satisfaction before the first European television satellite is launched in 1986 or '87.
Last month, the 10-nation European Community (EC) took its first timid steps in the field by proposing new legislation that would control what TV advertisers could and could not do.
In a ''green paper,'' the EC said that each country should be free to adopt any rules for broadcasts originating from that country but not for ''cross frontier'' broadcasts originating elsewhere. The paper also said that tobacco product spots should be absolutely prohibited and those for alcoholic beverages should be restricted.
''Some form of authority'' should review cross-frontier commercials before they're broadcast and enforce a ''code of practice,'' the paper said. This code would cover advertising that could be offensive to religious groups and children.
Also being considered by EC officials are rules that would prohibit TV advertising on Sundays and holidays. In addition, the EC is reviewing the possibility of limiting TV advertising to a maximum of 20 percent of total broadcast time.
The European business community, although skeptical about any new rules that would cramp their style, has nevertheless come out in favor of common standards that would be applied throughout Western Europe and prevent an atmosphere of unfair competition from developing.
''What we don't want,'' according to Paul de Win, director general of the Brussels-based International Union of Advertisers Associations (IUAA), ''is for the consumer's right of choice to be limited by new regulations.''
At the national level, all EC member countries - except Luxembourg - have moved long ago to ban TV advertising altogether or at least control the volume and content.
But the situation varies widely from country to country. Only Denmark and Belgium forbid advertising outright, although the Belgian government continues to look the other way on ad-inundated cable programs piped into the country from neighboring nations. Quite severe restrictions exist in the Netherlands and West Germany. Somewhat less strict rules apply in France; Luxembourg and the U.K. are even more liberal.
Some pro-business groups, such as the 25-nation IUAA, have said that until common standards are agreed to, the rules in the broadcasting country should apply to trans-frontier broadcasts. But consumer groups, arguing that it will be the viewers and not the producers who will be offended by objectionable ads, have said the receiving countries should have the final word.