Following the development of T5 lamps with merely 16 mm of discharge tube diameter, the discharge mechanism in high-frequency operation needed to be optimised, either for maximum luminous efficacy (hight efficiency, OSRAM abbreviation FH, PHILIPS abbreviation HE) or for maximum luminous flux (high output, OSRAM abbreviation FQ, PHILIPS abbreviation HO). The consequence was the emergence of lamps with identical length, but varying performance (see lamp table) and thus varying electrical characteristics for ECG required for operation. This was followed by geometrically identical circular T5 lamps of varying performance levels.
The hazard of confusion is impossible to avoid, which is why it is vital to pay close attention to the luminaire's type plate when replacing lamps.
Multi-lamp ECG for T5 lamps eliminate this issue. They recognise the connected lamps and their performance as well as further operating data.