The City Council of Berkeley, California last night unanimously voted to require electronics retailers to warn customers about the potential health risks associated with radio-frequency radiation emitted by cellphones, setting itself up to become the first city in the country to implement a cellphone "right to know" law. "If you carry or use your phone in a pants or shirt pocket or tucked into a bra when the phone is ON and connected to a wireless network, you may exceed the federal guidelines for exposure to RF radiation," the notice, which must be posted in stores that sell cellphones, reads in part.