RS Pro Substrate Low Profile Transformer The RS Pro Substrate Low Profile transformer is a low voltage transformer with twin 115 V ac 50/60 Hz primary windings. This board transformer is compact, low in height and has independent secondary windings ideal for series/parallel connections, providing output voltage and current options. This transformer is 100% electrical/flash tested and provides two compartment bobbins, high efficiency/low temperature rise, low inter-winding capacity and low radiation noise.