Dimming system

A variety of systems for dimming the stimulus lights (and sometimes the tone/noise generator) exist.

•	No control is possible over the intensity of the stimulus lights; they're either on or off.

•	No control is possible over the intensity of the tone/noise; it's either on or off.

Box type 2: nine-hole box with "old" dimming system (e.g. Cambridge Cognition / Campden Instruments 80600 [rat] and 80610 [mouse] Nine Hole Box Operant Chamber)

•	Each of the holes has an 'A' line and a 'B' line controlling its lamp (so, hole 1 has lines known as LAMP1A and LAMP1B, for example).

•	There are two manual dials in the box (not under computer control), labelled DIAL A (or V1) and DIAL B (or V2).

•	For a given hole, if the A and B lines are both off, then the stimulus light is off.

•	For a given hole, if the A line is on and the B line is off, then the stimulus light is on at full power. The FiveChoice task refers to this as dimming level 0.

•	For a given hole, if the A and B lines are both on, then the stimulus light is on with its intensity as set by the V1/A dial.The FiveChoice task refers to this as dimming level 1.

•	For a given hole, if the A line is off and the B line is on, then the stimulus light is on with its intensity as set by the V2/B dial.The FiveChoice task refers to this as dimming level 2.

•	No computer control is possible over the intensity of the tone/noise; from the computer's point of view, it's either on or off. Noise intensity may be controlled manually by setting it within the box.

Box type 3: nine-hole box with "new" dimming system (e.g. Cambridge Cognition / Campden Instruments 80600A [rat] and 80610A [mouse] Nine Hole Box Operant Chamber)

•	In this box, there is one control line for each stimulus light and one for the tone/noise generator.

•	A variety of intensity control systems are possible, but the factory-set one (which is the most flexible, and which the FiveChoice task assumes) allows 8 levels of intensity control from full power through to minimum power, plus off.

•	Three lines (DIM2, DIM1, DIM0) control the intensity for all devices. DIM2 is the most-significant-bit, and DIM0 is the least-significant bit (so, for example, if DIM2 was on and the others were off, we would write this in binary as 100 and call it the decimal number 4).

•	The DIM lines can be set to 0 (full power) through to 7 (maximum attenuation, but still on). When a device (lamp or tone/noise generator) is turned on, it comes on with an intensity as specified by the DIM lines.

•	For lights, intensities 0-7 represent 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30% respectively (where 100% approximates a 24V, 3W bulb).

•	For the tone/noise generator, intensities 0-7 represent 105dB, 100dB, 95dB, 90dB, 85dB, 80dB, 75dB, 70dB (the Campden documentation is vague as to the meaning of "dB"; perhaps dB SPL?).

•	Once a device is switched on, it is recommended to leave the DIM lines unmodified for 5 ms (as of June 2008 according to Campden; the FiveChoice task supports this as a configurable parameter, but [as of 13 June 2008] defaults to 10 ms for an extra safety margin).