As shown in the top diagram on this slide, when a user is designing a PCB without an I/O expander, all necessary signals must be routed directly from the processor to some logic devices, which in turn interface with the external device. This type of layout requires a large amount of board space, becomes tedious in trying to correctly lay it all out, and ends up being an expensive approach. In contrast, when designing a PCB with an I/O expander, all that needs to be done is to connect the SDA and SCL lines from the processor to the I/O expander, which in turn feeds directly to the external devices. This type of implementation is highlighted in the lower diagram. The advantages for an implementation of I²C with I/O expanders are very clear; allowing for easy board routing, board area savings which is crucial in portable applications; and pin savings from the processor. I/O expanders reduce overall material cost, and since the I²C protocol is an industry standard, it can be implemented in a myriad of applications.