DALI line power supply
The first mandatory system requirement is the DALI line power supply. This device is current limited and enables DALI devices to communicate on the line without having to use their own power.
One of the early prerequisites of DALI was that the line could be wired alongside the mains supply without any need for special segregation. The simplest way to achieve this was ensuring that the DALI wires were optically isolated away from the internal circuitry of a DALI device or controller.
The process of optically isolating the DALI control signal in essence created a problem of supplying power to the line. This problem was solved with the introduction of a DALI line power supply, this allows for DALI devices to utilize the line power to communicate on the line.
Another advantage of the DALI power supply is the ability to power devices such as switches and sensors from the DALI line without the need for any other power supply.