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Guide to DDC

Chapter 1:Input Output (IO) Basics

Digital Inputs

A digital input typically consists of a power supply (voltage source), a switch and a voltage-sensing device (analog-to-digital converter). Depending on the switchs open/closed status, the sensing device detects a voltage or no voltage condition, which in turn generates a logical 0 or 1, on or off, alarm or normal or similarly defined state.

Circuit Diagrams

The following circuit diagrams are examples of commonly used digital input configurations.

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