Commutators — Standard and PRO
Devices that carry the tether through an animal's rotation so the cable does not wind up — passive and mechanical in the Standard, motorized with active torque compensation in the PRO.
What winds up, and why it matters
A freely moving animal turns. The tether does not, so torque accumulates in the cable until something gives: the animal's behaviour changes to avoid the pull, the connector at the head takes the load, or the recording picks up the movement. A commutator puts a rotating joint in the path so the cable above turns with the animal and the cable below does not.
Passive or motorized — the whole decision
Standard is mechanical. An off-center tether attachment converts the animal's rotation into torque that turns the rotor, so nothing has to be powered or sensed. 42 × 42 × 87 mm, a 3.2 mm mounting hole, plug-and-play. Up to 256 channels per cable on recording headstages and 32 on stim-record.
PRO replaces the passive mechanism with a low-noise motor and continuous active torque compensation, which means the animal never supplies the force that turns the rotor. Torque is sensed either from an animal-side gyro/IMU on a 34 AWG bundle weighing under a gram, or from a rotor-side Hall encoder — the choice is whether you can afford any sensing mass on the head.
| Standard | PRO | |
|---|---|---|
| actuation | mechanical, passive | motorized, active compensation |
| power | none | plug-in, ~6 h on battery |
| XR channels / cable | 256 | 256 |
| XSR channels / cable | 32 | 64 |
| Neuropixels ports | — | up to 4 |
| GPIO | — | up to 9 |
| size | 42 × 42 × 87 mm | 99 × 105 × 150 mm |
| mass | — | 800 g |
The trade is plain: the PRO removes the force the animal has to supply and adds channels, ports and instrumentation. It costs size, mass, and a power connection. A preparation where the passive box turns freely enough does not need the motor.
Mixed-probe sessions
The PRO carries up to four Neuropixels ports and can stimulate through passive probes while recording Neuropixels in the same session — a dual-mode a single-probe-type rig never needs and a mixed lab cannot work around. It connects over USB-C to XDAQ or an imec-compatible system, validated with imec 5 m and Kontex 1 m cables, and takes Intan headstages and controllers through adapters.
Practical
5 mm passthrough for the tether bundle. Mounting by bottom thumb-screw or a 1/4-inch camera mount, so it goes on standard rig hardware.