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The chart below lists pinsouts for the ILDA DB-25 connector. Projectors use a male DB-25M connector and signal sources like Merlin, Pangolin or Babette hardware use a female DB-25F connector. The ILDA standard uses differential signals to provide increased immunity to induced noise and hum. For example, you will see X+ and X- signals defined below. The positive indicates a normal signal; the negative indicates an inverted signal.

What is a differential voltage?

A differential voltage is the voltage between the normal signal line and the inverted signal line. For example, if pin 1 (X+) is +3V and pin 14 (X-) is -3V, then the X signal's differential voltage (X+)-(X-) is +6V.

Differential signals are used because they are much more immune to noise than "single-ended" signals. Any noise induced in the signals -- say, from running the cables next to AC power cords -- will be cancelled out when the normal and inverted signals are added together in a special differential reciever circuit.

Where to connect X and Y

There are two types of scanner amps. For this discussion we'll talk about the X signal; the Y signal works the same but of course uses different pins:

• Single-ended amps have two input lines per signal, such as "Ground" and "X". Examples include Catweazle and Laser Media. With these amps, connect the Ground (pin 25) and the +X (pin 1) lines. Do not connect the -X (pin 14) line.

• Differential amps have three input lines per signal, such as "-X", "Ground" and "+X". Examples include Cambridge, GS MiniSax and TurboTrack. With these amps, simply connect the appropriate lines on the QM2000: -X (pin 14), Ground (pin 25) and +X (pin 1). On Merlin connect the Ground (pin 25) and the +X (pin 1) lines. Do not connect the -X (pin 14) line.

Where to connect intensity and color

If you have a single-color projector, use the Intensity/Blanking line (pins 3 and 16). If you have a multiple-color projector, use the appropriate color lines (pins 5-10 and 18-23).

Just as with scanner amps, intensity/color drivers can be divided into two types. With Merlin you'll use Ground and normal (+). However, note that the way you connect the QM2000 to single-ended scanner amps is different than the way you connect to single-ended drivers. In the former case, you'll use Ground and normal (+); iin the latter case, you'll use inverted (-) and normal (+).

For this discussion we'll talk about the "Red" line, but the other signals work the same way of course.

• Single-ended drivers have two input lines per signal, such as "Ground" and "Red". Examples include A+A, MVM and NEOS (4-channel driver). With Merlin connect the (pin 25) to the driver's "Ground", and the +Red (pin 5) to the driver's "Red". With the QM2000's connect -Red (pin 18) to the driver's "Ground", and the +Red (pin 5) to the driver's "Red". There is a gyrator circuit on the QM2000 which causes this connection to output in the range 0 to +5V.

• Differential drivers have three input lines per signal, such as "-Red", "Ground" and "+Red". Examples include NEOS 6- and 8-channel drivers. With Merlin connect the (pin 25) to the driver's "Ground", and the +Red (pin 5) to the driver's "Red". With the QM2000 simply connect the appropriate lines on the QM2000: -Red (pin 18), Ground (pin 25) and +Red (pin 5).

Where to connect ground

The ground line (pin 25) should be connected to the ground on your projector. This may be accessed through the projector's connector, or you may have to physically ground to the projector's case, or the third (grounding) pin on the projector's electrical cable.

Ideally, the cable going from the QM2000 to the projector will have its shield (wire mesh or foil wrap around the cable) connected to the ground line (pin 25). But you should still be OK even if you are using prebuilt cables such as standard parallel extension cables, and you don't know whether the shield is connected to the ground.

Note on interlock lines A and B

The purpose of the two interlock lines is so that a projector can tell when it is properly connected to an ILDA-compatible signal source.

The projector will put a current or signal into pin 4. The same current or signal should be present back at the projector when reading pin 17. (This is because pins 4 and 17 are connected together on the QM2000 board.)

If no current or signal is seen on pin 17, it means the DB-25 connector is not plugged into the projector.