"Mo-om, your office is on the phone, and I'm still finding out about my homework."

"Can you hold on please? I'll have to get off my other line in order to take down the information."

"Aunt Alice, can I call you back? I'm on long distance on the other line."

Sound familiar? Then you are either a member of one of the Washington-area households -- more than 30 percent -- with Call Waiting, or you've been talking to someone who has it.

Call Waiting, which has been available for the past 15 years, lets you know, with a clicking sound, that someone else is trying to call you when you are using your phone. By pressing your receiver button, a second call can come in, putting the first on hold.

"Of the four custom-calling services (now called IQ services) we offer, Call Waiting is by far the most popular," says Al Berman, manager of public relations for C&P of Maryland.

But it also apparently is socially incorrect. Judith Martin, in "Miss Manners' Guide for the Turn-0f-The-Millennium," deems it "rude," and sniffs, "Why anyone would pay extra for the privilege of offending current callers while having to make this explanation {that one's line is busy} oneself, Miss Manners cannot imagine."

Being able to receive a call from the school nurse while arranging Cub Scout meetings is one of the reasons Arlene Movit of Springfield has it.

"It's annoying when my conversation is interrupted," acknowledges Movit, mother of three school-age sons. "But it's also annoying when someone doesn't have it, and I can't get through to them."

Being able to get any business or personal calls with teenagers in the house is another reason for Call Waiting's popularity.

"I couldn't live without it," says Carol Wooster, mother of an 18-year-old daughter and two younger children. "And I'm having a hard time living with it."

It is inexpensive ($3.50 a month), easy to use and convenient but, according to Berman, "Some of our customers do dislike being put on hold."

Bonnie Obermayer of Oakton, Va., mother of a college-age daughter who also has it on her telephone in the dorm, is one of them. "I hate Call Waiting. I'm having it removed. I'd rather people got a busy signal. Let them call back."

Telephone rules -- whose calls are more important, how long one can stay on, when it is appropriate to make and receive calls -- the whole issue of "etiquette" regarding children, adults and the telephone is difficult enough. With Call Waiting, it's compounded.

It only takes one time of having your child say, "Oh, by the way, Dad, your office called while I was on the phone. They needed to talk to you immediately," or "Mom, while I was talking to Jean, some editor from New York called. She won't be able to get back to you for two weeks," to realize some new rules need to come along with that ubiquitous "click."

According to Myra Stalling, "Manners for Minors" instructor at the McLean Community Center in McLean, it is very simple.

"Children need to be taught that adult calls always take precedence. Children can't, and shouldn't, determine on their own the importance of a call for an adult. They simply need to tell their friend they'll call them back -- quickly, no chitchatting -- and hand the phone to the adult."

But what about in the business forum? Call Waiting also is a very popular and inexpensive option for small businesses and home offices.

"The chaos in someone else's life does not designate a crisis in mine," says Adina Conn of Adina Conn Associates, a design editorial and marketing consultant firm in the District. "I believe each client should feel that they are the most important to me. It's a distraction to the clients."

For Paul Driessen of U.S. Media in Annandale, it's a real plus. "I like it," says Driessen, "especially if I'm on a call that's important, but I'm expecting another important one. I don't want to lose either one. More and more people understand that it saves a lot of 'phone tag.' "

Paul and Sarah Edwards, authors of "Working From Home, Everything You Need to Know to Live and Work Under the Same Roof," agree. They acknowledge the inconvenience, yet "weighing the pros and cons, we are solidly in favor of Call Waiting. ... It's no less disruptive than putting someone on hold to answer a second line." In an article in "Home Office Computing Magazine," the Edwardses suggest following some simple rules of etiquette:

Don't ignore the Call Waiting signal. They recommend politely excusing oneself to take the second call, and returning to the first call in less than one minute. What if the second call actually is more important than the first? The Edwardses recommend explaining the situation to the first caller, briefly, taking the second call, then returning that first call as promptly as possible.

"Honesty, forthrightness and concern seem to help make Call Waiting work," they conclude.

That presumably eliminates claiming you've just received another call when it really hasn't beeped, ignoring the beep when you think it is someone you are trying to avoid, or "forgetting" to pass on a message to someone that came in while you were on a call.

Now if someone could just explain why phone calls always seem to come in series -- three hours of no calls, then, as soon as you start a conversation ... Call Waiting clicks.

As with the answering machine and voice mail, Call Waiting fits that category of technology we don't want to live with but, increasingly, can't seem to manage without.

Please HoldTone

"Tone Block," a free "Call Waiting enhancement," allows temporary blocking of Call Waiting. It first was instituted for modem users (to protect their computer transmissions from being interrupted or lost) but works just as well when one is about to make a normal telephone call.

To activate Tone Block on a push-button telephone with Touch-Tone service, push *70 (asterisk70), then dial the number as usual; from a rotary telephone, dial 1170, then dial the number as usual.

Tone Block must be activated before each call as it only blocks one call at a time.