| 摘要 |
A circuit arrangement comprises a controller (20) for producing a control signal selectively indicative of normal and diagnosis modes. Responsive to the control signal, an IF stage (12) processes desired RF and diagnosis input signals into an IF signal of an IF level. Responsive to the IF signal and a reference signal of a reference level squelch signal producing circuit (15) produces a squelch signal when the IF level is lower than the reference level. First and second signal generators (26, 27) generate first and second threshold signals of first and second threshold levels, respectively. The second threshold level is lower than the first threshold level. Responsive to the control signal, a switch circuit (22) selects the first and the second threshold signals as a selected threshold signal. A line (29) supplies the selected threshold signal to the squelch signal producing circuit as the reference signal. |
