======================BEGIN QUOTE====================
There is a rather "expensive" box that was designed for
use to adapt early Sony chagners to non changer equipped head
unit (Sony or otherwise).
It has a unit link cable to connect to the changer, power
cables for input, RCA cables for input and output and antenna
connector "T" so you can use it as an "RF" type unit if you
want.
=====================END QUOTE=========================
There is actually the RM-X69RF CD changer controller which normally provides
RF output but, if you plug the changer's RCA outputs into the head unit's
AUX input, you can avoid the need to use the RF modulator.
I have discussed this unit previously in a posting on the 4th September and
will repeat it heare incause you missed it. As cited by Timothy P. Stockman,
there is an undocumented +12 volt trigger output on the RM-X69RF controller,
which is exposed as a red wire and a blue wire on the power MOLEX connector.
The situations that I documented were for various implementations, some of
which are common in the Australian market.
These are:
1. The stereo car radio that doubles as an amplifier for an outboard
cassette deck (common in a lot of Nissan / Datsun, high-end Mazda and some
Mitsubishi vehicles made during the 70s and 80s)
2. The stereo car radio-cassette (OEM or aftermarket) that provided an AUX
input for an add-on single-slot CD player (a practice common with some cars
sold during the late 80s and early 90s where the CD player was supplied as a
dealer option).
In most of these installations, it was necessary for the outboard CD or
cassette player to turn on the head unit whenever one intended to play the
CD or cassette. This would bave been done in one of many ways:
1. The CD player or cassette deck would expose a +12 volt "trigger current"
to an "trigger input" in order to wake up the radio and accept signals from
the deck.
2. The CD player or cassette deck would use TTL logic or an extra pole on
the "cassette-present" microswitch to short an input trigger loop to ground
in order to wake up the radio and accept signals from the deck; in a similar
way that a cellular-phone system triggers a car stereo's phone-mute circuit
during a phone call.
3. The same device may use Method 1 or 2 to wake up the radio (if you don't
have to turn the radio on manually to make use of it) but use a switch or
relay to select between the radio's own signal sources or that device's
signal.
The trigger output could be wired across the trigger input with systems that
work on Method 1; wired across a relay that shorts the trigger input to
ground in a Method 2 system and/or a DPDT relay that manually selects the
signal between the RCA outputs on the stacker and one of the existing
sources.
This information listed here is especially of interest to Australian readers
who maintain older vehicles with their OEM sound systems and want to add
MiniDisc or CD to their vehicles. The only units that may not be easy to add
extra equipment to are those units that use a proprietary serial bus chosen
by the vehicle builder usually in order to discourage the use of cheaper
aftermarket equipment.
With regards,
Simon Mackay
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