[IggleSniggle]

Not in telecommunications, but I do know that there are synchronous comm networks that don’t require any kind of sentinel / delimiter because there is a guarantee that the voltage will agree.

My signals background mostly comes out of music, so somebody else probably has a better answer. But any time you need to convert between digital and analog signals relatively seamlessly, ie, introducing minimal processing overhead, you’re going to run into these kinds of issues. In that regard, you can think of telecoms as a CPU, and just like in a computer, you need a system clock that the entire architecture agrees on.

First likely application that comes to my mind is VoIP.

[sennight]

It is one of those problems that is really easy to ignore, until you can't. I was using a cheapo 8051 based logic probe the other day and had a lot of fun dealing with not only jitter of two different oscillators (probe + device under test) - but differences in response time between probes (within the same sample period). If you ever find yourself wondering much influence your MCU's 4 clock cycle per instruction architecture has on the waveforms you're looking at... you're about to have a very bad time.