Human brainwave activity is too subtle to read unless the signal is amplified. These units available now usually connect through a USB port and transmit signals to the therapist computer. Older units use a serial interface.

EEGer4 Neurofeedback software supports a variety of EEG amplifiers, each with varying signal characteristics.

Details of these amplifiers are documented in the EEGer4 Technical Manual, available here [PDF].

• The linearity has to do with how evenly the amplifier "amplifies" the incoming EEG.
• The bandwidth tells how low and how high in frequency the amplifier can pass data.
• The ideal amplifier would linearly amplify all frequencies of interest.
• Connections to the computer can be either serial (wired or Bluetooth) or USB.