A single HAL1 device contains a fixed number of inputs, outputs, RAD ports, and so on. If you purchased a HAL1 but you need more than four RAD ports, you can attach the EXP1 Expansion Unit to your HAL1 and suddenly have eight more RAD ports in your system. Remember that you can also connect DRs to RAD ports, so you could use the EXP1 to expand your DR connections as well.
The EXP1 Expansion Unit connects to a HAL1 via a FireWire cable, which is similar to a USB cable and does not require IP addresses. The only limitation when using FireWire is its maximum cable length of 15 feet. Given that the purpose of the HAL1 Expansion Units is to expand the host device capabilities within a single rack room, this FireWire distance limit should not pose a problem.
In addition to connecting the physical Expansion Unit hardware to your HAL device, you must also add the Expansion Unit to your HAL configuration.
note: You can connect a maximum of four EXP1 Expansion Units to a HAL1 device.