General form:

UXXXXXXX n1 n2 n3 mname l=len <n=lumps>

Examples:

U1 1 2 0 URCMOD L=50U
URC2 1 12 2 UMODL l=1MIL N=6

n1 and n2 are the two element nodes the RC line connects, while n3 is the node the capacitances are connected to. mname is the model name, len is the length of the RC line in meters. lumps, if specified, is the number of lumped segments to use in modeling the RC line (see the model description for the action taken if this parameter is omitted).