MPI resistor switch

why The network MPI must have resistance at the end of the line generally included in the connector and activated by a simple switch...
regards
haoon

MPI is a protocol.
Similar to Profibus, Modbus, DH485, etc etc etc.

RS 485 is the underlying electrical interface, ie the physical layer, upon which all these protocols are used.

So to answer your question:

"Ideally, the two ends of the cable will have a termination resistor connected across the two wires. Without termination resistors, reflections of fast driver edges can cause multiple data edges that can cause data corruption. Termination resistors also reduce electrical noise sensitivity due to the lower impedance, and bias resistors (see below) are required. The value of each termination resistor should be equal to the cable characteristic impedance (typically, 120 ohms for twisted pairs)."

Taken from Wikipedia