The biosignalsplux 4-channel hub comes with 4 analog channels which allow you to connect up to 4 analog sensors simultaneously (see green check marks below).

The remaining channel is reserved for use of a common reference electrode (for example for multi Electromyography (EMG) acquisitions) or to connect 1 digital sensors (e.g. FNIRS, SpO2).
4-channel hubs are included in the following kits:
Important Information
Some analog sensors my provide multiple individual sensor signals, which all require their own dedicated port. This can reduce the total number of sensors you can connect to your Hybrid-8 hub.
Example: One Accelerometer (ACC) provides 3 individual signals (1 for each axis) and requires the use of 3 of the available 8 hybrid channels, leaving only 5 open for additional sensors.