ActiveThree: Smaller, lighter, and faster active electrode EEG

We are often asked one of several different flavors of this question. The version of the question people ask tends to depend on their preferred code development platform. People want to capture live data, manipulate it in some way, and either act on the data as it comes in (closed loop applications, such as brain-computer interface or neurofeedback), or just display and/or store the data in some way that is unique to their intended use of the system. They ask:

• Can I read an ActiveThree BDF data file as it is written without interfering with the performance of the data acquisition software?
  • Yes, but the technique is not documented anywhere by Biosemi. Most important to know is that a BDF data files is closed after each block of data is written, so there is a window of time for reading the file between writes, and the length of that window depends on the speed of your computer processor, speed / efficiency of your storage medium, and your selected sampling rate (indirectly set by choosing a decimation ratio in ActiView).
• Does the ActiView software have a built-in mechanism to stream full bandwidth live data over a network in a generic form that I can capture and manipulate with my own software in C#, Python, MATLAB, etc?
  • Yes. See this forum thread for details.
• Is there an SDK for ActiveThree?
  • Yes, there is an SDK. See this page for SDK details. However, note that the SDK was written for ActiveTwo, and some special knowledge is needed to adapt it for use with ActiveThree. Biosemi has been willing to share additional details on a case-by-case basis.
• Is LSL supported by ActiveThree? Or, is ActiveThree supported by LSL?
  • ActiView 10.2 and above for use with ActiveThree has an LSL server built-in. There is no need for a third-party Biosemi plugin. However, for ActiView 9.X and earlier versions for ActiveTwo, a third-party plugin was distributed with the Lab Streaming Layer distribution on GitHub.
• Is Biosemi’s ActiView software open source?
  • Earlier versions of ActiView (9 and below, for ActiveTwo) were offered with LabVIEW source code. As of this date, no announcement has been made about whether source code for ActiView 10 will be made available.

So, for the most part, the answers to the various formulations of this question are “YES”.

ActiveTwo users who are interested to stream live Biosemi data to Python should check out Ted Burke’s blog post at:

This example shows how to use Python to capture live data streamed from ActiView using the built-in TCP server. His code was developed for ActiView for ActiveTwo, but ActiveThree also has a built-in TCP streaming function, so it should be possible to adapt Ted’s example for use with ActiveThree as well.

A new ActiView version 10.3 and AD-box firmware version 2.2 are available for ActiveThree systems.
The combination of this new acquisition software and firmware enables support for Lab Streaming Layer

ActiView 10.3 has native LSL support, and no extra plugins or further software is required. ActiView 10.3 functions as an LSL server, and all regular ActiView functions (display, saving to BDF file, etc.) remain operational during LSL streaming. All installed EEG channels as well as the connected sensor channels are streamed to LSL, with the sample rate selected in ActiView. The preprocessing for the auxiliary sensors is performed in ActiView.

LSL streaming is handled by a separate software thread to prevent delay and jitter by the main display/saving-to-file thread. In addition, the instantaneous backlog value is transmitted for each streamed data package to allow LSL to compensate for computer processing delays. The backlog is the time between the moment that a sample is stored in the intermediate ring buffer by the USB driver and the moment that it is read from the ring buffer by the LSL streaming thread in ActiView. Latency and jitter values below 10 millisecond can be achieved this way.

Native LSL support in ActiView 10.3 greatly simplifies the synchronized acquisition from ActiveThree along with other measurement devices supported by LSL.

If you have an ActiveThree system and are interested in using LSL, contact us about whether your firmware version would need to be updated to support this functionality.

ActiveThre is provided with drivers and host data acquisition software for Windows computers only as of May 7, 2025. This could change in the future, but we are not aware of any plans to support additional operating systems.

Note that certain applications, such as event-related potentials, often require a separate computer to run experimental control / stimulus delivery software. The requirement for a separate computer for stimulus delivery is more a function of the experimental control software needing full control of computer resources to do its job.

In brief, the computer requirements for the ActiView data acquisition software and USB interface driver are:

• Operating system:
  • Windows 10 / 11
• RAM: 16 GB or more
• Hard Drive: recommend 1 TB SSD, but user should anticipate free space needed for data (file size in bytes is approximately = 3 X AD rate in Hz X number of channels X number of seconds recorded)
• Display: 1920 x 1080 or higher resolution display
• One free USB 2.0, USB 3.0 or USB C port
  • SPECIAL NOTE ABOUT USB CHIPSETS: Small form factor computers without PCIe expansion slots should be avoided. The Intel W480 chipset found in many brands of small form factor desktop computer is not capable of keeping up with USB 2.0 High Speed data rates, which prevents operation in speed modes 2 and 3 for AD boxes that have high speed firmware installed. This is of particular importance in systems used in settings where ABR and cortical ERP will be measured concurrently or alternately. If you opt for a small form factor computer, be sure to use a computer that has at least one free PCIe expansion slot that you can add a PCIe expansion card with one or more USB 2.0 or higher ports.

Note: The ActiveThree computer DOES NOT NEED A PARALLEL PORT.  A parallel port on the experimental control computer can be used to send stimuli to ActiveTwo, but we provide a USB virtual serial port trigger cable with every new system, so a parallel port is not needed for triggering.

In addition, the following are recommended for the ActiveThree host computer:

• Network interface and remote storage for data backups
• Accessories such as an extra monitor / keyboard / mouse, extension cables, etc to permit access to the EEG display from the separate room for the subject

• ADC type – ActiveThree uses a 24 bit SAR ADC, while ActiveTwo uses a 24 bit Delta-Sigma ADC. This SAR ADC provides a cleaner frequency response without spurious tones that can occur with Delta-Sigma ADCs and may impact ones ability to distinguish signal from noise at certain frequencies in FFR paradigms.
• Number of channels — ActiveThree has a maximum of 136 biopotential channels plus six auxiliary sensors. ActiveTwo has a maximum of 264 biopotential channels plus four auxiliary sensors.
• High frequency response – ActiveThree has a low-pass antialiasing filter at 5.4 kHz, while ActiveTwo has a low-pass antialiasing filter at 3.2 kHz.
• Battery type – ActiveThree uses a single Li-ion battery cell, while ActiveTwo uses a multi-cell Lead-acid battery unit. This new battery type supports the use of modern low voltage components and greater power efficiency.
• Auxiliary sensors for ActiveThree require no installation of new internal components — all that is needed is already built-in. All you need to do is purchase the sensor and plug it in. The software automatically detects what is plugged in and displays/saves the sensors being used. ActiveTwo requires internal sensor couplers to be installed inside the AD box, and the user needs to select the desired sensors on the Sensors tab.
• ActiveThree’s CMS/DRL circuitry was redesigned for improved suppression of interference from a wide range of ubiquitous high-frequency interference sources.
• Weight – ActiveThree’s AD box weights 1.76 lbs with the battery, and ActiveTwo weights 2.4 lbs with the battery.
• Size – ActiveThree’s AD box measures about 6.4 X 5.9 X 2.4 in with battery, and ActiveTwo’s AD box measures about 4.7 X 5.9 X 7.5 in with battery.