| 摘要 |
Test apparatus enables the relative timing of two signals picked up by probes 16, 18 to be determined. The two signals are fed, via switchable polarity and level changing circuitry 10, 11, 13, 14 to a simple flip-flop 12, which comprises two cross-coupled transistors plus two input transistors. With both inputs at 0, the flip-flop is in an abnormal state with both cross-coupled flip-flops in the same state. The first input signal to go to 1 causes the flip-flop to enter a corresponding one of its two normal states (the cross-coupled flip-flops in opposite states). Detection circuitry 24 and display means 15 signal this state. A low frequency bias oscillator 20 shifts the sloping transitions of one signal up and down relative to the other, changing their relative timing. For a part of each slow cycle dependent on the relative timings of the two signals, their effective timings at the flip-flop will be reversed. Hence the mean output from 24 will be dependent on the time difference between the two signals. |
