Liv Ullman looks at her telephone, her eyes wide with panic. "If you didn't love me," she murmurs into the receiver, "this telephone could be a frightening weapon -- a weapon that left no trace, made no noise."

In Jean Cocteau's "La Viox Humaine" ("The Human Voice"), which will be shown at 9 tonight on Channel 26, Ullman spends an hour onstage, all alone in her bedroom with her telephone. "I'm not used to sleeping alone any longer," she says to her departed lover. And a moment later she is explaining why she avoids mirrors, why she leaves the light off now when she goes to the bathroom: "Last night, I found myself face-to-face with an old woman."

An hour after seeing Ullman speak these lines, viewers will see them sung by soprano Karan Armstrong in a head-on confrontation between opera and spoken drama.

Cocteau's 1930 play (which Francis Poulenc adapted into an opera in 1959) could hardly be simpler. A man and a woman have lived together. Now he is leaving and being a decent sort, has decided to do it gradually so it will hurt less -- like cutting off a dog's tail an inch at a time.

As the play (or opera) opens, the woman is alone onstage, the man has moved out but promised to phone. She spends most of the next hour talking (or singing) into the phone, her emotions ranging from "I am being very brave" to fits of hysteria and veiled threats of suicide (which she has already tried once, unsuccessfully). At the end, he hangs up for good and she murmurs (or sings) "I love you, I love you," into the dead phone, over and over again as the curtain comes down.

This Cocteau-Poulenc double-header offers viewers a rare opportunity to make a direct comparison between opera and straight drama in a single, intensive session with an almost clinical prescision. Poulenc adapted the Cocteau play with a very light hand -- for all practical purposes, the two texts are identical (though they are shown tonight in slightly different English translations).

But they are two radically different approaches to the same material. And, for television at least, the approach to the opera by director Barbara Karp is likely to win more favor than the approach to the play by director Jose Quintero. This is not a fault Quintero, who is an excellent director, or Ullman, who wrings from the script every drop of emotion it contains or implies. But the play is presented as just that -- a play that happens to have a couple of cameras present. For the television medium, a solid hour of Liv Ullman in a single setting, looking like a slightly underweight Rubens goddess talking into a telephone and playing with a few props, tends to become too much of a good thing.

From the opening shots the operatic production announces that it is more ambitious. The camera pans over a photo of a man (clearly the faithless lover), and then to make everything perfectly clear it lingers over a newspaper whose headline announces (in French) "Actress To Marry Lawyer." As the opera goes on, the treatment shifts frequently into voice-over with flashbacks showing the mand and woman together in happier times, the woman spying on a railroad-station scene as the man has a rendezvous with the actress, the woman's attempted suicide, and a harrowing scene where she stands outside his house in the rain watching the man and the actress together.

At the end, as the last scene begins to fade into the closing credits and the music slowly dies, Karp adds a final touch. There is a previously unnoticed, small red spot on the woman's nightgown -- can it be blood? The camera moves slowly back until it becomes clear that she has killed herself.

Some may find this directorial, intervention in a classic work of art heavy-handed -- and there is no question at all that Karp has altered the concepts of Cocteau and Poulenc. But it works and, considering the medium, it was probably necessary.

Karp has successfully translated to film an opera that offered serious difficulties. With added (silent) characters and scenes, it is no longer a tour de force -- but in losing that precious quality, it gains enormous impact. t