Access control systems are the foundation of any security system. However, it is important to keep it as simple as possible because with additional modules and increased complexity, they get more and more difficult to manage and maintain. This causes a hassle of their own.

Access control systems have come a long way in providing security, both in terms of the physical shape of the devices as well as the technology that accompanies them.

This blog talks about the two security protocols that access control systems use: OSDP and Wiegand to help you understand their differences, and find out which one is better for your usage.

How Do Access Control Systems Work?

Access control systems are used to manage entry and exit to and from a premises. It could be an office complex, a construction site, parking lot, truck yard, or even schools and universities.

Whatever the application, access control systems grant user access based on a set database. If the user credentials match the database, the user is granted access.

An access control system consists of three major components:

  • User Credentials: This varies depending on the type of system installed. It could be a key fob, a key card, biometric verification, or mobile access credentials.
  • Access Reader: This is the device installed near a door that reads the credentials of the user in question and transmits data to the controller.
  • Access Controller: This is the central hub of the access control system. For smaller systems, this is contained within the reader, but for bigger systems, it is a separate device that verifies user credentials, authorizes access and communicates it to unlock doors.

Access Control Protocols: Wiegand and OSDP

Access management can be done in various ways. The technology behind it can also vary. Two prominent technologies used in access control systems are the following:

  • Wiegand
  • Open Supervised Device Protocol (OSDP)

Wiegand Protocol For Access Control

wiegand access control

Wiegand is a dated technology named after its inventor John Wiegand. It has been a prevalent access control protocol for decades. It is essentially a wiring standard that dictates how an access control reader communicates with a door controller.

How A Wiegand Format Reader Work

A Wiegand protocol is based on a two-wire system that consists of two data wires and a ground wire. Multiple other wires are used for the reader LED, buzzer or any other device that needs to be connected to the system. The Wiegand protocol can be used to transmit up to 32 bits of information. The entire procedure goes as follows:

  • When a user credential is entered into the reader (could be a card, fob or any compatible format), the reader recognizes the information stored on the card.
  • The reader converts this information into an analog signal composed of 0s and 1s according to the Wiegand interface. This is then carried to the controller.
  • The reader drops and raises voltage according to the signal of the credential. This change is read by the controller and interpreted to authorize access.

The data on such a card is permanently written on it and cannot be changed or reprogrammed.

Open Supervised Device Protocol (OSDP) For Access Control

Osdp access control

OSDP is a fairly new access control communication standard developed by the Security Industry Association (SIA). It is an open standard protocol that offers a significant improvement over the Wiegand and allows greater communication and operability of access control devices. Used by modern access control systems, it is able to provide improved security through its 128-bit AES encryption when communicating between devices.

How A OSDP Format Reader Works

OSDP makes use of the RS485 communication standard and is a two-way communication protocol that lets the controller communicate back to the reader as well. Here is how it works:

  • When a card or fob is held to the OSDP reader, it reads the information on the card and transfers it to the controller.
  • The controller then communicates back to the reader to authorize access to the site.

The OSDP protocol allows greater communication between devices which means it is easier to provide user feedback on the access attempts that improves user experience of the access control system.

Difference Between Wiegand And OSDP Access Control Systems

There are a wide variety of differences between Wiegand and OSDP protocols. The following table describes them in detail:

  OSDP Wiegand
Protocol Uses RS485 to transmit digital data to the controller. This offers secure and reliable two-way communication between devices. Relies on analog signals to offer one-way communication from the reader to the controller.
Wiring It requires two wires for transmitting and receiving data. It consists of two wires for communication, a ground wire and other wires for additional features you want to enable.
Encryption It offers 128-bit AES encryption to improve system security. It offers no encryption and data can be intercepted by anyone.
User Feedback Can transmit acknowledgements for users when access is requested. It offers no feedback about transmission or access attempts.
Tamper Alerts It constantly monitors the connection to ensure that it is not tampered with. t is easy to tamper such a system, making it vulnerable to thieves.
Support for Biometric Devices It offers support for biometric verification. It does not have data transfer capability to enable biometric verification
Remote Updates Can be updated remotely. Does not offer remote updates.


Wiegand and OSDP both have their own uses depending on the business site requirements, user preference and budgetary restrictions.

Reasons to choose OSDP Platform For Access Control

OSDP being the newer technology offers certain benefits over the older Wiegand. Here are the reasons why you could choose to go for an OSDP platform for access control:

Multiple Profiles

OSDP comes with a wide variety of modes or profiles to choose from. These have been developed by the Security Industry Association (SIA) as a standard protocol for connecting devices to communicate. It is a globally recognized protocol for access control devices which means greater interoperability between different security systems.

The profiles enabled through OSDP are the following:

  • Basic
  • Secure
  • Smart Card
  • Biometric

Easy Installation

Since OSDP does not require so many wires, it takes up much less space, is easier to set up and configure compared to Wiegand. This means you get all the functionality like buzzer, alarm, user feedback etc. without putting in additional wires in your system.


Because of the obvious savings of wiring and installation, getting an OSDP-enabled access control system is more cost effective. It saves up on material costs (wiring) as well as human capital (installation labor).

Tamper Resistant

In addition to being AES 128 encrypted, OSDP can also notify users of physical tampering in real time because the connection is being constantly monitored. This real-time alert improves security and helps take swift action.

Better User Experience

As it allows user feedback from the same wire, it improves the user experience of the entire system. It lets the user know when an access attempt has been registered or when access has been granted.

Looking For Access Control Systems In Canada?

If you are in search of reliable access control systems to secure your business in Canada, Spotter Security has your back. Spotter Security, with over 20 years of experience in the security industry, knows the ins and outs of securing a business site. From security cameras, to access control, to alarm systems and live monitoring, Spotter Security keeps you confident about your site security while providing 24/7 technical support should you ever encounter problems.

The OSDP and Wiegand technologies are both in use as of today. It depends largely on which systems fit your needs and budget. Be sure to consult a security company to help you decide the right access control systems for your business.

Written by : Carlo Di Leo

At the age of 24, with no experience in the security industry or any money in the bank, Carlo quit his job and started Spotter Security from his parent's basement. Founded in 2004, Spotter grew from a single man operation into a multi-million dollar security system integrator that caters to businessess and construction sites across Canada.

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