If you are talking about the charging plug for any JR tx (the plug you plug into the tx with the Tx side of your JR wall chargers) then the centerpin is negative. The negative lead from your charger must be attached to the center pin of this plug when used in JR Txs.

The is opposite of all others except possibly Spectrum. That is why when using another brand wall charger the tx side (Tx side only) of that charger musthave the polarity reversed.

John