Some counter/timers have an external trigger input but I have never used such an input so maybe someone can help me?
I've read it can be used for timing the opening (and/or closing?) of the counter gate after 1 to n pulses at the trigger input and after an optionally delay.
What is the most important use case for such an external trigger input?
How precise must the time relation between the trigger pulse and the opening of the gate be? milli seconds? micro seconds? nano seconds?