Frequency indicator fitted to motor vehicle radio - displays reception frequency and has detection stage incorporated in adaptor fitting into antenna socket

摘要

The frequency indicator has an inductive coupling circuit for determining the oscillator frequency, a frequency divider circuit, a processing circuit and a display. The inductive coupling circuit and the frequency divider are housed in an adapter fitting into the radio antenna socket and itself providing a socket (6) into which the antenna plug is inserted. A lead (3) extends from the adapter to connect the inductive coupling circuit and the frequency divider with the remainder of the frequency indicator circuit. Pref. the coupling circuit and the frequency divider are formed as IC's mounted on a circuit board (7) incorporated in the adapter between the antenna pin (5) and the antenna socket (6).