11 CFR 100.28: Telephone bank (52 U.S.C. 30101(24)).

Telephone bank means more than 500 telephone calls of an identical or substantially similar nature within any 30-day period. A telephone bank does not include electronic mail or Internet communications transmitted over telephone lines. For purposes of this section, substantially similar includes communications that include substantially the same template or language, but vary in non-material respects such as communications customized by the recipient's name, occupation, or geographic location.