| 摘要 |
PURPOSE:To narrow the occupied band width of a transmission signal by using the first reference frequency as a comparison frequency in a receiver, and decoding information on the basis of the difference between a frequency train inputted next and the reference frequency. CONSTITUTION:A tone generating circuit 15 has a reference frequency f0 and corresponds information to a difference with the frequency f0. An output of the circuit 15 is converted into a high frequency signal at a frequency converting circuit 17 and transmitted from an antenna 5. A signal received by an antenna 6 is supplied to an intermediate frequency amplifier circuit, its output is fed to a frequency converting circuit 19, the output of which is converted easily into a frequency band processed by a frequency analysis circuit 20. A signal corresponding to the frequency f0 is outputted at first from a filter among filter groups and inputted to an information decoding circuit 21. Then, the frequency difference from the frequency f0 is discriminated depending on a signal representing from which filter the signal comes and an output circuit 14 is driven. |
