An interface circuit and an external circuit

An interface circuit suitable to be used with an external electronic ballast, the external electronic ballast adapted for fluorescent or halogen lamps, the interface circuit comprising:

• an input to be coupled to the external electronic ballast;
• a primary power winding electrically coupled to the input;
• and
• a data transceiver circuit comprising:
• a primary data winding;
• a primary load across the primary data winding;
• a primary load modulation circuit electrically coupled to the primary data winding and adapted to modulate the primary load across the primary data winding in response to a first data signal to be transmitted via the primary data winding;
• and
• a primary data detection circuit electrically coupled to the primary data winding and adapted to detect a second data signal from a signal induced on the primary data winding,
• wherein the primary power winding and the primary data winding are magnetically coupled together and adapted to be magnetically coupled to a secondary data winding (30) of an external circuit.