25-09-2020, 08:39 AM
(24-09-2020, 01:43 PM)ppppenguin Wrote: Strictly speaking there are no such things as digital signals. They are all analogue. In many cases you can treat signals as digital but sometimes you can't. XDSL carried on copper pairs is very definitely analogue.
I am not sure if you were referring to my mention of 'digital signal' here but yes, I realise what you mean and do understand the later comments. By digital signal I meant in effect the digital representation of the analogue signal as it is received, which is perhaps the essence of later comments. This particular intercom system implementation did have guidance and the outside door intercom unit itself did come with a length of cable, the instuctions stating that under no circumstances should the cable be extended which probably took into account impedances and reflections etc.
From the top level / system view though many signals are digital. For instance FSK is obviously analogue in implementation but digital in design.
Tracy
