| 摘要 |
PURPOSE:To attain the ease of listening by using a reception section of a digital radio equipment to decide the intensity of a received electric field, there by switching a time constant of a delay circuit and quickening or slowing down the voice mute of a squelch circuit in response to the intensity of the electric field. CONSTITUTION:An electric field level received by an antenna (not shown) is detected by a detection circuit 11, the level is inputted to a comparator 14, where the level is compared with a reference voltage set by resistors 12, 13. When the level is larger than the reference voltage, the comparator 14 outputs an H level. Upon the receipt of a frame pattern from a received data, a frame synchronizing detection circuit 15 outputs an H level. The output of the frame synchronizing detection circuit 15 is subjected to a delay by a delay circuit 16 and sends a mute signal of a received voice. When the output of the comparator 14 is at an L level, an off-delay of a mute signal is prolonged and when the output is at an H level, the off-delay is reduced. Thus, the frequency of intermission of a voice due to fading at a weak electric field is reduced, the end of call noise at an intensive electric field is reduced and then the listening state is improved. |
