How does a computer distinguish two separate transmissions on a wire

My basic idea of networking at the lowest layer is that one computer will send a bunch of parallel bits at a time down a cable and another computer will read these bits. For example, computer #1 sends a bunch of parallel bits to computer #2. Computer #2 then gets the bits then waits for the next bunch of bits. And so on.

I have a couple of questions about how this works and how we get around a few problems.

Problem #1: Say Computer #2 doesn't wait long enough for the next series of bits. Computer #2 may accidentally read the first set of bits twice, messing up communication.

Problem #2: Computer #2 waits too long. It doesn't read the second set of bits in time and only starts reading after the second set of bits are shown.

[to summarize problems 1 & 2, it seems like it would be very difficult to exactly sync the rate of transmition between the two computers)

Problem #3: We can't rely on every transmission to be different. So it's not like we can just wait for the transmission to change and then store the new value.

Problem #4: Say we use a special phrase. So after every transmission computer #1 signals to computer #2 that the transmission is going to change by flashing a bunch of 1's. This is a problem because what if our data is a bunch of 1s? We won't know if the transmission changed or not.

The only solution I can think of is to have some extra bit that alternates for each transmission, bit this seems like it wouldn't work for one-bit-at-a-time transmission networks like wifi. What part of all of this am I missing? How is this problem solved in the real world?

• It seems this is about the electrical engineering part of networking, so might be off-topic here. Commented Sep 8, 2017 at 5:34