By far the best-known and most controversial system is "caller identification."

Phone companies in nine other states and Washington are seeking to introduce caller identification.

Telephone companies argue that a blocking feature would defeat the purpose of caller identification.

Mandatory caller identification will reduce the value of an unlisted number.

Many phone systems already block calls that do not display caller identification.

Is caller identification a blessing that will help protect consumers from obscene and other unwanted calls?

Using caller identification, the company can inform the police of the location of the computer if it is reported stolen.

First there was caller identification, which allows people to see the number of the phone from which the call was made before they answer.

Long-distance companies also offer caller identification to some businesses with 800 and 900 numbers.

Most phone companies have resisted such blocking, although California now requires it if caller identification is introduced there.