Abstract: Frequency encoded signaling method and structure to correct for frequency error introduced in the generation of encoded signals. A sequence of frequency encoded signals are recorded on rotating magnetic recording devices in telephone offices in conjunction with recorded announcements. The signals identify the types of announcements. Speed variations in the different recording devices introduce frequency errors in the reproduction of the signals, hindering their automatic decoding. This problem is solved by recording a reference frequency signal with the encoded signals on the recording devices. A receiver detects the signals and measures the difference between the expected reference signal frequency and the received reference signal frequency.