This becomes a problem when designers attempt to delay signals with higher frequency characteristics than the delay line is capable of passing. A change in the input waveform caused by variance in the group delay can significantly affect accuracy, especially at higher frequencies. Specifications should always include the applied frequency and intended use to ensure that suppliers provide the appropriate delay lines. Crucial mistakes can be avoided simply by exercising caution when specifying a delay line. Failing to specify the falling-edge accuracy is probably the most common omission.
Many designs require a specific pulse width from input to output.
Waveform of rising and falling edges of the pulse and leading and trailing edges of the positive and negative pulses. Identifying leading and trailing edges requires determining whether the reference pulse is positive or negative. Similarly, specifying input frequency is often affected by duty cycle, pulse width, and pulse spacing. It is important to ascertain whether the pulse is negative or positive to ensure proper performance. A matching polarity must be specified to ensure that the delay line will perform according to optimum specifications.