An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size.
- A compressor encodes data (e.g., audio/video/images) into a smaller form (See codec.)
- An audio encoder may be capable of capturing, compressing and converting audio
- A video encoder may be capable of capturing, compressing and converting audio/video
- An email encoder secures online email addresses from email harvesters
- A PHTML encoder preserves script code logic in a secure format that is transparent to visitors on a web site
- A multiplexer combines multiple inputs into one output.
8b/10b encoder used for fast speed in communication system
Job positions 
- A Data Entry Encoder may enter data from phone surveys in a coded format into a database.
- A Data Entry Encoder may enter payment amounts from legal tender documents from financial institutions into a database.
- A Manual Encoder may manually scan code tags on baggage that were missed by an automated system.
- A device or person that encodes or encrypts military messages, such as the ADFGVX Cipher in WWI or the Enigma device in WWII.
- A Microchip hopping encoder integrated circuit for non-fixed-code secured entry.
Medical encoding software 
- EncoderPro searches ICD-9-CM, CPT, and HCPCS Level II medical codes, to increase accuracy and allow ease of auditing for compliance.
Transducers (such as optical or magnetic encoders) sense position or orientation for use as a reference or active feedback to control position:
- A rotary encoder converts rotary position to an analog (e.g., analog quadrature) or digital (e.g., digital quadrature, 32-bit parallel, or USB) electronic signal.
- A linear encoder similarly converts linear position to an electronic signal.
Such encoders can be either absolute or incremental. The signal from an absolute encoder gives an unambiguous position within the travel range without requiring knowledge of any previous position. The signal from an incremental encoder is cyclical, thus ambiguous, and requires counting of cycles to maintain absolute position within the travel range. Both can provide the same accuracy, but the absolute encoder is more robust to interruptions in transducer signal.
Electronic circuits 
- A simple encoder assigns a binary code to an active input line.
- Priority encoders establish the priority of competing inputs (such as interrupt requests) by outputting a binary code representing the highest-priority active input.
See also 
- Line code
- Redundancy in databases
- Television encoding: NTSC, PAL and SECAM
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- asic-world's Digital Combinational Logic (part III) - an overview of encoders in circuitry.