VSS500N12 
12kV Pulse generator, 1.2/50us, as per IEC 60060, 500ohm impedance and low energy
VSS 500N12.1
12kV Pulse generator, 1.2/50us, as per IEC 60335, 40ohm impedance and low energy
VSS 500N12.6
12kV Pulse generator, 1.2/50us, as per IEC 61180-1, 50ohm impedance
VSS 500N12.7
12kV Pulse generator, 1.2/50us, as per IEC 60950, 13 ohm + 25 ohm impedance, special pulse circuit,