The Purifier is an accessory product. Suppose you only connect the Purifier with the power plug. In that case, the Purifier will not work because it can’t receive the instruction to boot without the connection with the 4-pin plug. Likewise, if you only connect the Purifier with the 4-pin plug, the Purifier will not work too because it is not powered. For safety reasons, the Purifier is off by default when powered.