What's a Loxone and why does the stupid thing have such a low input impedance? The reason is this chip. HVS882. It's an industrial input serializer chip. The input impedance is only 10k. This chip operates in a "window" mode for detecting "on" vs "off". With the recommended 4.7k pullup on a 24V supply, this leaves things very close to the 16V threshold that the chip requires for an "on" state. So I've started using 3.9k pullups which gives a little more room for movement on longer cable runs where a few volts can potentially be lost bringing it under the required 16V.