| 摘要 |
The invention provides an apparatus for receiving electromagnetic signals with an improved capability to trace free or occupied channels. The invention comprises an assembly having a first frequency filter for filtering frequencies in a reception channel, when the apparatus is in the reception mode, or for testing one or more transmission channels, when the apparatus is in the tracing mode. The invention furthermore comprises a second frequency filter and a first switch for optional selection of the transmission or reception band. The change from the reception mode to the tracing mode is carried out, for example, by means of switches, and the bandwidth of the tuning of the oscillator, which provides a reference frequency by means of which the received signals are converted to an intermediate frequency, is reduced. This allows a particularly fast changeover.
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