Washington ? News of missing children will speed to the public over radio, TV and electronic highway signs in more states under the Amber Alert legislation, signed Wednesday by President Bush.

Already operating in 41 states, such networks quickly distribute information about kidnapped children and their abductors.

“It is important to expand the Amber Alert systems so police and sheriff departments gain thousands or even millions of allies in the search for missing children,” Bush said at a bill signing ceremony in the White House Rose Garden.

“Every person who would think of abducting a child can know that a wide net will be cast,” he said.

Watching Bush sign the measure, which also includes stiffer federal penalties for crimes against children and gives prosecutors new tools to fight child pornography, was a tearful experience for the mother of the bill’s namesake, 9-year-old Amber Hagerman who was kidnapped in 1996 and never came home.

It was a happier day for 15-year-old Elizabeth Smart, a teen from Salt Lake City who was making her first public appearance since being found in March, nine months after she was kidnapped at knifepoint from her bedroom. Smart smiled shyly and offered no words.

Tears rolled down the face of Amber’s mother, Donna Norris, as Bush spoke of signing the legislation in memory of her daughter.

“It’s bittersweet,” said Ms. Norris, who wore a button with the face of her daughter, who was abducted in Arlington, Texas, and later was found murdered. “It’s a chance to save other children’s lives and I’m proud of it.”

The new law strengthens federal criminal penalties for child pornographers, sexual abusers and kidnappers.

President Bush is surrounded by rescued kidnap victims and family members as he signs a wide-ranging package of child safety measures in the Rose Garden of the White House. Among those gathered Wednesday were Rick Hagerman and Donna Norris, at left in the front row, the brother and mother of Amber Hagerman, for whom the Amber Alert system is named. Behind them are Elizabeth Smart, who was rescued in March nine months after she was kidnapped from her Salt Lake City home, and her parents, Lois and Ed Smart.