If you are doing a difficult DCC install such as installing a speaker into the tender of a steam loco you have probably already worked out that its better to use a little plug and socket so that the tender and loco can still be separated.
Micro Plug & Socket Connector For Hornby Tender Connection, Bachmann Oxford Rail
Micro Plug And Socket Loco To Tender Connection, Hornby, Bachmann, DCC Sound Etc
2 pin micro plug and socket (pre-wired) 5 pack
4 pin micro plug and socket (pre-wired) 5 pack (compatible with Hornby X6113)