Do you mean you're looking for a 12 volt supply?
These are the connections on the back of the unit:
http://i.imgur.com/aqIrS9B.jpg
From memory, I think 'SAFE' is permanent 12 volts and UB+ is ignition-switched ... perhaps someone else could verify.
If I understand correctly what you're attempting to do though, I would highly recommend using and XCarLink unit instead, which will give you a 3.5mm jack input, a USB charging socket and a bluetooth connection to the RNS-D, all without sacrificing the CD connection.
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Mark
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2002 FE S8 Ebony Black Pearl
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Cars Owned:
The Tesla Era: 2020 Model S Performance Ludicrous+ (present)
(Black, with all black premium interior and carbon fibre décor, 21" sonic carbon twin turbine wheels and FSD capability)
The Audi Era: '97 A8 4.2 (Ming Blue) --> '96 A8 4.2 QS (Dark Green) --> '02 FE S8 (present)
The Citroen Era: '84 BX 1.6 RS --> '89 BX 1.9 DTR Turbo --> '94 XM 2.0L Turbo --> '96 XM 2.0L Turbo Exclusive --> '00 Xantia Activa 2.0L Turbo
The Banger Era: '76 1.2L Lada VAZ-2101 (Ruski Fiat 124) --> '80 1.7L Morris Ital HL, finished in Ermine White and Rust