Hyperscanning trigger interface
 
The Hyperscanning Trigger Interface gives Hyperscanning possibilities to any Active3 system.
Besides that, it also offers all the normal functionality of the standard BioSemi Trigger Interface.

With Triggered Hyperscanning (Active3), each subject has its own AD-box and acquisition PC. The experiment is started by the Master PC. The data is synchronized with standard UTP cables connected to the Hyperscanning Trigger Interface. A Triggered Hyperscanning setup can contain an unlimited number of AD-boxes.

For the Active3, we moved on to the method with the Triggered Hyperscanning because it has the following advantages:
- The timing accuracy of Triggered Hyperscanning is similar as compared to the timing accuracy obtained with optical Hyperscanning (Daisy-chain).
- There are no hardware changes required to enable Triggered Hyperscanning (no installation of the extra optical receiver input is necessary)
- With Triggered Hyperscanning, the AD-boxes do not need to be in a specific Speedmode. (optical method needed selection with Speedmode switch)
- Triggered Hyperscanning works up to 16 kHz (Optical Hyperscanning was limited to 2 kHz)
- Triggered Hyperscanning offers an unlimited number of AD-boxes in the chain (Optical Hyperscanning was limited to four AD-boxes)
- Triggered Hyperscanning works over various platforms/devices. The Master should be an Active3, but the other devices can be any system that can read in at least 2 trigger lines and has a known file format (e.g. Active3, ActiveTwo, various fNIRS systems, various Eyetrackers, etc.).
 
BioSemi Hardware generated time-stamps VS Software generated time-stamps:
BioSemi Hyperscanning synchronization using hardware-generated triggers is superior to the method where synchronization is achieved with software-generated triggers (for example LSL, Lab Streaming Layer.
Both methods are based on the same basic idea: insert timing markers into both data streams and synchronize the data streams afterwards based on these time stamps. The fundamental difference is that BioSemi inserts the time stamps in hardware: triggers are generated by the USB receiver based on the AD-box master clock, and read by the trigger inputs of the Active3 USB Receiver and other devices. Software-generated timestamps on the other hand generate the time stamps in the acquisition PC and insert them into the data streams in the computer. This means that the time stamps are inserted after the damage has been done. USB transfer, driver, buffering and Windows all can and will affect the timing. This makes the Hyperscanning synchronization method with software-generated time stamps essentially flawed. With the BioSemi method, the synchronization accuracy is only limited by the duration of a sample.
 
Ordercode: Hyperscanning Trigger Interface
Price: 500 Euro
 
 

All the acquisitions PCs are set to "Hyperscanning" with a switch in ActiView10. One of the PCs should be set to Master, the other PCs should be set to Slave.
The rest is automatic: when the Master starts saving data to file, the Slaves follow automatically.
The standard UTP cables (not crossover) may be connected to either of the 2 UTP connectors of the USB Receiver.
Only the 'master' AD-box (AD-box 1) needs to be an Active3 AD-box. All 'slave' AD-boxes may be an ActiveTwo, Active2.5 or Active3 AD-box.
The file merger in ActiTools is used to merge all the separate files into 1 bdf file.
The info that is entered in every acquisition PC in ActiView when starting the 'save file' will Identify each AD-box in the merged .bdf file.
   
  How to use the Hyperscanning Master and Slave file Merger?
 

After you have succesfully recorded the data of 2 (or more) AD-boxes, you can use ActiTools100 (or newer) to merge Hypersampled files.
For this example, we will use 2 AD-boxes. The data of AD-box1 was recorded by PC1. The data of AD-box2 was recorded by PC2.
During the recording of the data, the USB Receiver of PC1 had a Hyperscanning Trigger Interface connected and PC2 also had a Hyperscanning trigger Interface connected.
Each Hyperscanning trigger interface was connected with a standard UTP network cable to either of the 2 UTP connectors of the other Hyperscanning Trigger Interface.
After the recording is completed, the 2 files can be checked with ActiRead902 (or newer). Both .bdf files should show recorded triggers on trigger channels 15 and 16.
Trigger channel 15 becomes high when the Master PC starts the synchronisation and becomes low when the Master PC stops the synchronisation.
Trigger channel 16 is high every second.

Now open ActiTools100 and go to the tab-page: "Hyperscanning Master and Slave file Merger"
There click "start" and browse to the Master file (PC1). After that, ActiRead will ask for the second file, and you can browse to the slave file (PC2)
ActiTools will now automatically generate the merged file, with all data of both AD-boxes synchronised into 1 file with a synchronisation accuracy higher than 1 sample per second.
If you have more than 2 AD-boxes, then again run the Hyperscanning Merger to add the other AD-boxes.

Below you can find 2 example .bdf files that you can use as test files:
- Sample file 1 (PC1). With electrode sets in a bucket of water.
- Sample file 2 (PC2). With no electrode sets connected.