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What is OSDP in Access Control? A Complete Guide.

Access control systems are essential for ensuring the security and safety of a building or facility. They allow authorized individuals to gain entry while keeping unauthorized individuals out. OSDP, which stands for Open Supervised Device Protocol, is a communication protocol specifically designed for these access control systems. It offers advanced features and benefits, making it a popular choice for many organizations.

Understanding OSDP is crucial for anyone involved in physical security, from system administrators to security professionals. This guide will cover everything you need to know about OSDP, including its key features, advantages, and how it compares to other existing protocols.

What is Open Supervised Device Protocol (OSDP)?

The Open Supervised Device Protocol (OSDP) is a communication protocol that is used to interface a control panel or security management system with peripheral devices such as card readers, keypads, and biometric readers. It is an open standard protocol that provides advanced security features and enhanced functionality compared to older protocols like Wiegand.

This protocol allows for bi-directional communication, enabling devices to exchange information and receive commands, enhancing access control systems' functionality and flexibility. OSDP offers improved security, reliability, and interoperability, making it a more advanced and preferred choice for access control device communication.

What are the Three Critical Components of OSDP?

OSDP provides a framework for controlling and monitoring access to physical spaces to ensure the security and efficiency of various facilities. It has three critical components, each playing a vital role in its overall functioning.

Access Control Systems

Access control systems allow for the monitoring and management of access permissions, as well as the logging of entry and exit activities. With OSDP, supported access control systems (such as the NetBox™ and OnGuard® systems) can communicate and exchange data securely and efficiently, ensuring that only authorized individuals can access certain areas, preventing unauthorized physical access and potential security breaches. 


OSDP readers are devices that interact directly with the users, such as card readers, biometric devices, or keypads. They are responsible for capturing user data and sending that information to the controller for processing. 


OSDP controllers are responsible for managing and controlling the communication between the readers and other devices in the system. They act as the intelligence in the field and make local decisions on who should and should not have access to areas within the facility.

What is the Difference Between OSDP Communication & Wiegand Communication?

The OSDP enables bi-directional and secure communication between the access control panel and the reader. In contrast, the Wiegand communication is an older and simpler protocol that is one-way communication with no encryption or security. Over the last several years, there has been an ongoing transformation in these types of technologies. Although both protocols transmit data for access control, there are distinct differences between OSDP and Wiegand communication.

  OSDP Wiegand


Utilizes the RS485 protocol for transmitting card format data from the reader to the controller. This protocol is highly reliable and offers secure communication between the devices.

Relies on an older and less robust protocol for passing card format data, which can be susceptible to interference and has known security vulnerabilities such as replay attacks.


Uses a two-wire communication system, where one wire is responsible for transmitting data, and the other wire receives the data.

Consists of two data wires to transmit card format information. It also uses many other wires for control of reader LEDs, Buzzer, and more.


Provides a secure and encrypted method of communication used in access control systems.

Does not provide any encryption.


Provides supervision, which means that it constantly monitors the communication between devices to ensure they system is always online and available.

Provides no supervision, which can lead to potential vulnerabilities or communication issues going unnoticed.


Can provide acknowledgments (ACKs) and negative acknowledgments (NAKs) during the transmission process, which ensure that the data is successfully received by the intended recipient.

Does not provide any guarantees of successful transmission.

What are the OSDP Profiles?

The OSDP Profiles are modes of operations that define specific functionality for the protocol. These profiles, developed by the Security Industry Association (SIA), provide a standardized way for different devices and systems to communicate with each other, ensuring interoperability and compatibility. Here are the different OSDP profiles:


These devices are designed to replace Wiegand protocols and offer the added advantage of bidirectional communication. This bidirectional protocol ensures that the devices are protected from common person-in-the-middle attacks, where an unauthorized person intercepts and alters the communication data between devices. Basic does not include encrypted communication.


Secure devices that meet the Basic profile and can handle encrypted messages using Secure Channel are essential in ensuring the safety and privacy of communication. These devices can enter and exit both Basic and Secure modes as claimed, providing a seamless and secure user experience.

Smart Card

These devices that transfer structured data units necessary for smart card operations. This makes them ideal for use in various environments, such as Federal Identity, Credential and Access Management, as well as Personal Identity Verification. 


Devices, such as fingerprint scanners or facial recognition systems, have become increasingly popular for enhancing security measures. Many of these devices utilize OSDP messages to read and match biometric templates.

What are the Benefits of OSDP?

Increased Security and Encryption

OSDP offers several security features to ensure encryption and increase data security. These features include AES128 encryption, unique and diversified keys, supervision of data wires, and reader cover tamper notifications.

Automatic Tamper Alerts

With automatic tamper alerts, OSDP can detect and notify users of any physical tampering on the devices connected to the system. This helps enhance the system's security and enables timely response to potential threats.

Ability to Push Updates to Readers Remotely

With increased capabilities, OSDP can provide text notifications and messages to compatible reader displays, notify of reader communication errors or disconnects, and push configuration and firmware updates to readers from a centralized location.

Easier Deployment

OSDP offers a more efficient two-wire communication solution compared to the traditional six or more wires required by Wiegand. It provides enhanced third-party integration and standardization, as well as centralized management. Additionally, it supports multi-drop for both Anti-Passback (APB) or IN/OUT applications and allows for cable runs of up to 4000 feet.

International Standards Owned by SIA

The OSDP protocol is recognized and supported globally (IEC 60839-11-5), ensuring compatibility and interoperability between different security devices and systems. Having international standards owned by a reputable industry association like SIA helps to establish trust and credibility in the OSDP protocol, making it a reliable and widely adopted solution in the security industry.

4 Key Best Practices for Implementing OSDP

In order to implement OSDP successfully, there are four key best practices that should be followed. These practices will help organizations maximize the benefits of OSDP and ensure a secure and efficient access control system.

1. Install End of Line Terminating Resistors

To ensure proper functioning, the transmission line impedance should match the hardware impedance of the connected interface, which is 120 Ω. Termination is necessary to achieve this. Attaching a resistor between the signal lines at both ends of the transmission line accomplishes proper termination. When termination is not implemented, reflection can occur, causing the voltage to bounce back onto the line and distort the signal.

2. Use a Twisted Pair Wire

Twisted pair cables consist of two insulated copper wires twisted together to minimize electromagnetic interference (EMI) and crosstalk. Any external interference or noise is canceled out by twisting the wires, ensuring reliable and high-quality data transmission. This makes twisted pair cables ideal for OSPD applications, where data signals need to be transmitted over long distances outdoors.

3. Use an Overall Low-Capacitance Wire

By using a low-cap wire, which refers to a wire with a lower capacity for electrical current, it helps reduce potential interference or signal degradation. This is crucial for ensuring reliable and robust communication between devices within an OSDP system.

4. Use Stranded Cable

Stranded cables are made up of multiple smaller wires twisted together, which provides flexibility and durability. This ensures that the cable can withstand frequent movement or bending without breaking. It also provides greater resistance to breaking when terminating wires into a Terminal Block connector (which is common for Access Control panels). Stranded cables are also less prone to signal interference and offer better transmission quality than solid cables.

How LenelS2 Can Support OSDP Implementation

LenelS2 can support Open Supervised Device Protocol (OSDP) implementation through its range of security products. OSDP is an industry-standard communication protocol that allows for secure and reliable communication between access control devices like card readers and control panels. LenelS2 offers various security products compatible with OSDP, including access control readers, controllers, and software. These products can be easily integrated into an existing security infrastructure, allowing for seamless implementation of OSDP.

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Frequently Asked Questions About OSDP

Using OSDP is beneficial because it provides a more secure and standardized way of communication between access control devices and control panels. It allows for greater interoperability and flexibility in integrating various security systems, ensuring seamless and efficient access control operations. Furthermore, OSDP Secure Channel enhances cybersecurity measures by encrypting data transmission, minimizing the risk of unauthorized access and potential security breaches.

Some common mistakes when installing access control wiring include improper cable management, insufficient power supply, incorrect termination of wires, and inadequate grounding. These mistakes can lead to system malfunctions, security vulnerabilities, and higher maintenance costs.

RS485 is a communication standard for serial communication systems. It is widely used in industrial applications that require long-distance, robust, and reliable communication between multiple devices. RS485 allows multiple devices to be connected on a single bus, enabling communication over distances of up to 4000 feet. It uses differential signaling to minimize noise and electromagnetic interference, making it suitable for noisy industrial environments.