In this example, there is a multiplexer switching between RS-232, RS-485, USB 1.1, and an audio signal. A power supply with ±25V is used to cover the highest voltage signal range. In this case, it belongs to the RS-232. This means a multi-voltage solution is required to meet the ±25V and the +5V supply voltage to power the individual ICs. This can be done with either a single power supply with multiple outputs or a single power supply with extra regulator circuitry to provide the other voltage levels. This complicates the power supply design and takes up more space on the PCB for the boosted voltages, but fortunately Analog Devices offers a Beyond-the-Rails™ dual 4:1 MAX14778 multiplexer. This part eliminates the need for the high voltage positive and negative rails and simplifies the power supply to a single low voltage supply.