Check the listing for details. IET RC-Box RCS-500 Resistance-Capacitance Substituter. Condition: Used. Listed at 375.00 USD. The RCS-box combines the features and specifications of both the R-box and the C-box in one convenient package. Ideal for setting timers, oscillators, and filters, the resistance and capacitance may be used independently, in series, or in parallel. A shorting link allows them to be coupled or separated. One nice feature of the RCS Series is that it uses convenient side by side, color-coded, thumbwheel switches.allow for direct reading — There is no fumbling with multiple slide or rotary switches. Simply dial in the desired values and use! Made of high impact plastic and weighing less than a pound, these decade boxes are very portable and can reduce clutter on a busy lab bench. It is in very good condition and will be shipped fully insured.