A callbook is a directory of radio station call signs. Originally a bound book that resembled a telephone directory, it contains the name and addressees of licensed radio stations in a given jurisdiction (country). Modern Electrics published the first callbook in the United States in 1909.[1] Today, the primary purpose of a callbook is to allow amateur radio operators to send a confirmation post card, called a QSL card to an operator with whom they the have communicated via radio. Callbooks have evolved to include on-line 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 databases include QRZ.COM,[2] IK3QAR,[3] HamCall,[4] F6CYV,[5] DXInfo,[6] OZ7C[7] and QSLInfo.[8]