The URC model is derived from a model proposed by L. Gertzberg in 1974. The model is accomplished by a subcircuit type expansion of the URC line into a network of lumped RC segments with internally generated nodes. The RC segments are in a geometric progression, increasing toward the middle of the URC line, with (K) as a proportionality constant. The number of lumped segments used, if not specified for the URC line device, is determined by the following formula:

[\begin{array}{ll} {N = \frac{\log\left| {F_{\lbrack font\ rm\ \lbrack char\ m\ mathalpha\rbrack\lbrack char\ a\ mathalpha\rbrack\lbrack char\ x\ mathalpha\rbrack\rbrack}\frac{R}{L}\frac{C}{L}2\pi L^{2}\left| \frac{\left( {K - 1} \right)}{K} \right|^{2}} \right|}{\log K}} & \ \end{array}]The URC line is made up strictly of resistor and capacitor segments unless the ISPERL parameter is given a nonzero value, in which case the capacitors are replaced with reverse biased diodes with a zero-bias junction capacitance equivalent to the capacitance replaced, and with a saturation current of ISPERL amps per meter of transmission line and an optional series resistance equivalent to RSPERL ohms per meter.