Think of an electronic system. It contains many blocks. The lowest level block contains many other structures (Transistors, opamps, capacitors etc.) that one page is nearly enough for it to be fit into. Lets call it 'X'. This X contains A, B and C blocks. So I labeled them as A1, B1 and C1.
second level contains lots of other stuff and lots of X's. Here is the question. Since I drew X and labeled its substances as A1, B1 and C1, how can I show that I am using seperate X's in second level structure? I can not label every substance like A2, A3, B2, B3 bla bla... Also, this substances are doing different duties. So how can I show it in drawings?