Product Details – 130B1130 VLT® A/B in C Option Adapter MCF 106 The A/B in C Option Adapter can be placed in the Option C slot and allows for up to four A and B-options in different combinations. Limitations are due to the facts – that the drive cannot handle more than one fieldbus at the time, cannot handle several identical options, and that the physical layout of options can cause limitations. VLT® Relay Card MCB 105 and VLT® PTC Thermistor Card MCB 112 are not supported by the adapter and must thus only be installed in the standard slot B of the Control Card.