Hybrid equivalent circuit generally includes 1. Simple hybrid circuit, 2. Load hybrid circuit.
The equivalent circuit can be calculated after the simple hybrid circuit can be directly connected in series and parallel.
The circuit can be seen intuitively: R2 is connected in parallel with R3, then in series with R1, then in parallel with R4.
Complex hybrid circuits need to be equivalent by punctuation method.
It is not easy to see the serial-parallel relationship of the circuit mentioned above. Different labels are marked at different positions and the same labels are marked on the same wire.
Then, find the resistance from A to B, from A to C, and from C to B.
Draw the equivalent circuit diagram.
You can see that R2 is in parallel with R3, and then R4, and then R1 as a whole.