Analog multiplexers have sets of switches that connect several analog inputs to a common analog output, allowing a single analog-to-digital converter (ADC) to sample data from multiple inputs. Often, analog multiplexers are designed for routing pulse height analysis (PHA) data from multiple amplifier/detector circuits through a single ADC. Some analog multiplexers accept a serial input or can operate with only one power supply. Others can be enabled or disabled by applying a logic signal to the chip enable (CE) pin. Analog multiplexers with bilateral switching, fault-tolerant protection, on-chip electrostatic discharge (ESD) protection, and over-current protection are also available. There are two main European Union (EU) standards or certifications for analog multiplexers: End of Life Vehicles (ELV) and Restriction of Hazardous Substances (RoHS).