| 摘要 |
Reception or non-reception of a signal is detected on the basis of whether or not a certain noise level is reached at the receiver output. Measuring periods are formed, during each of which the charge of a capacitor changes from a fixed value to a value dependent upon the momentary noise. The time from the beginning of the measuring period until a certain state of charge is reached is compared with a reference time, and a receive criterion is produced when the time dependent upon the noise is shorter than the reference time. The reference time may be obtained in a manner similar to the way in which the first-mentioned time is produced. When both times are thus obtained in an analogous manner, not only the presence but also the absence of a signal can be detected much more rapidly than heretofore. |
