resistor canbus

Hi, can anyone tell me what the purpose is of the ending resistors on a Canbus line? What could happen when one is not at the end but somewhere in the middle.

Termination resistors on a transmission line reduce reflections from an open end of the line. The value is usually equal to the characteristic im[pedence of the tranmission cable.

Thanks Bernie, what do you understand under reflections? ( my technical englisch is not that good )

In simple terms: In high speed digital communications, the end of a wire can act just like a mirror, bouncing the signal back down the wire. The reflected signal "over writes" that data that is coming down the wire. Obviously, this can be a big problem with fast serial type communication networks.

Reflection is a phenomenon that occurs with all high frequency signals. That's the reason why you can't use a 50 Ohm coaxial cable for you TV set: the characteristic impedance of TV like systems is 75 Ohm. On the other hand: you can't use the 75 Ohm coaxial cable from your TV set to use it in a coaxial ethernet installation because that system uses a characteristic impedance of 50 Ohm. Everything you use on a high frequency system has to have the right characteristic impedance: cables, connectors, taps and so on.

If you want to know more of this phenomenon: search a ham (radio amateur) in your neigbourhood. They can explain everything about it. You don't have to pay them, just provide them a couple of .

Kind regards,