TB1
TRSS - you pay for the rating up front (or with a bank loan which they help you arange)
They pay you back over 5 years(plus a bit to cover interest) if you leave, you are left with the loan.
Your salary is reduced by the amount they pay you back (about £5000 a year) from that of a non TRSS F/O.
In reality, you are paying for the rating over 5 years after which you go onto normal salary.( the amount is actually the same, but you have paid off the loan by then)
sounds confusing I know