Citizens band radio
From Wikipedia, the free encyclopedia
A callbook is a directory of radio station call signs. Originally a bound book that resembled a telephone directory, it contains the name and addresses of radio stations in a given jurisdiction (country). Modern Electrics published the first callbook in the United States in 1909. Today, the primary purpose of a callbook is to allow radio operators to send a confirmation post card, called a QSL card to an operator with whom they have communicated via radio. Callbooks have evolved to include online databases that are accessible via the Internet to instantly obtain the address of another amateur radio operator and their QSL managers. The most well known and used on-line QSL database for the 11 meter / freebander community is QRZ11.COM, designed after its "big brother" QRZ.com for amateur radio.
Wiki Link: https://en.wikipedia.org/wiki/Citizens_band_radio