Hi, you can buy a rj45 to bt socket jump lead.I would assume you require a master unit with capacitor this will enable you to wire your bell as standard BT wiring.
Note: if your rJ45 socket is on a patch panel be very careful as your bell circuit may cause issues on IT equipment.
When you say "phone system" - Is this a PBX presenting it's extensions on RJ45 sockets?
Every phone system would be different - Some use 1 pair per phone, and present 4 extensions on each RJ45 port. Some present hybrid extensions per port, using 3/4 as the voice/ringer and 2/5 as the data pair for the screen and BLF LEDs etc.
Every system is different, and either way, you will need to connect via a master socket.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local