Access control is the selective restriction of access to a place or other resource. Some access control system can connect to computer and serve as an attendance recorder. There are different types of access control system including the most traditional numeric keypad, sophisticated card reader and more advanced biometric (fingerprint recognition, iris scanning, etc) system: 進出控制系統是用來限制進出某場地或資料庫。部份進出控制系統可連接電腦及同時可用作考勤。進出控制系統有不同種類，包括最原始的數字密碼掣、精密的讀卡器及更先進的生物識別系統（指紋辨識、虹膜掃描……等）：

Although keypad is less secured than card reading system and biometric system, this most traditional access control device is still popular for its economy and simplicity.
最傳統的進出控制器材密碼掣雖然安全度較讀卡系統及生物識別系統低，但由於比較便宜及簡單易用，仍相當普遍。

Proximity card reader is the most popular sophisticated access control system. A proximity card can be "read" without inserting it into a reader.
非接觸式讀卡器為各精密進出控制系統中最被普遍使用的一種。讀卡器可感應卡的資料而無需把卡插進讀卡器。

Traditional access control system cannot identify the user personally. Biometric system can prevent fake use. Biometric System includes fingerprint recognition, palm reader, iris scanning, face recognition etc.
傳統進出控制系統無法杜絕盜用，用人體特徵（例如指紋）去辨別，便可杜絕盜用。生物識別系統包括指紋辨識、掌紋識別、虹膜掃描、人面識別……等等。