Stimulus delivery to recording electrodes or electrodes adjacent to the recording electrodes is likely to cause saturation with stimulation artifacts. Fast settle works to mitigate this, generally providing a shorter recovery from stimulation by improving cool down from saturation. Fast settle methodology is separate in front end amplifiers vs hubs/directs, but the end result is the same.

Front end amplifiers have two possible fast settle methods. Unmodified amplifiers shift the low corner of the hardware bandpass from 0.3 Hz to 300 Hz while the BNC receives TTL high. The filters are held high for the duration of the TTL plus an additional 140 ms after the TTL is low. Since the filters are shifted and there is no blanking, spikes will still be visible. A custom modification can be performed on amplifiers that uses a sample and hold method. The last value prior to receipt of the TTL pulse is held until the incoming signal to the BNC is low.

Hubs and Directs function differently in their fast settle. The signal and reference are tied together to zero out the signal and then return to normal when the TTL pulse is no longer high. On the Direct, the fast settle connector is tied to each digital headstage bank. On the Hub, the fast settle connector is tied to each HDMI input. The signal fed through the fast settle BNC is passed downstream so the digital headstage can receive a fast settle signal.

Fast settle is applied by feeding in the TTL high signal when the Cerestim is actively stimulating. This can be easily done by connecting the BNC on the amplifier, hub, or direct to the Cerestim sync port, or can be achieved by sending a TTL high signal from another source when the stimulation is known. The TTL pulse should stay high (5V) for the stimulation.