This Newlec extractor fan model incorporates an automatic condensation (humidity) sensor which switches the fan on when the condensation level builds up. Once the condensation clears the fan automatically switches off. Additionally, there is a pull-cord that can be used to override the humidity sensor and switch the fan on. It is normally used in toilets or bathrooms (outwith zone 2). This fan requires a permanent live and neutral (2 wires, excluding earth) connected to operate correctly.