A frequency reference, a time reference and data may be provided on, and subsequently extracted from, a single information stream. To achieve this a modulator 102 generates the single information stream by modulating the data on the frequency reference and pre-empting the data modulation to modulate...http://www.google.de/patents/US5577071?utm_source=gb-gplus-sharePatent US5577071 - Method for and apparatus to extract a frequency reference, a time reference and data from a single information system
