Sec. 5.152  Station identification.

    Each class of station in the experimental services shall, unless 
specifically exempted by the terms of the station authorization, 
transmit its assigned call sign at the end of each complete 
transmission: Provided, however, That the transmission of the call sign 
at the end of each transmission is not required for projects requiring 
continuous, frequent, or extended use of the transmitting apparatus, if, 
during such periods and in connection with such use, the call sign is 
transmitted at least once every thirty minutes.