- 8 -AC Power Pack+ ECinema Processor Center ChannelCenter Channel SpeakerORAC Power Pack75 OhmCoaxial CableAN INSTALLATION USING TWO IRC-21SConnect an IRP-20 power pack to each of the IRC-21s. From the unit receivingthe audio signal from a source, connect the RF OUT terminal to the RF INterminal of the second IRC-21 utilizing 75Ω Coaxial Cable. A power pack MUSTbe used for each IRC-21 so configured.There is, theoretically, no limit to the number of IRC-21s from a single sourcethat you may connect in this way.Within reason, distances between units is unlimited.INTERNALEXTERNALRF SOURCEONOFFINTERNALEXTERNALRF SOURCEONOFFUPC-21 INSTRUCTION MANUAL Ultra Stereo Labs, Inc.