calla969,
There are two types of transducers diplexed and non-diplexed. The CA50/200-1T is a non-diplexed version transducer.
So you need to know if the GARMIN 1243xsv will accept non-diplexed transducers, and if your Garmin 1243xsv doesn't accept any non-diplexed transducers, then you'll need to add a MB1100 Matching Box.
- Deep Blue