In addition to the repeating A or N modulation signal, each transmitting station would also transmit its Morse code identifier (typically 2 or 3 letters) once every thirty seconds for positive identification.[20] The station identification would be sent twice: first on the N pair of transmitters, then on the A, to ensure coverage in all quadrants.[2][note 4] Also, in some installations local weather conditions were periodically broadcast in voice over the range frequency, preempting the navigational signals, but eventually this was done on the central fifth tower.[3][note 5]