Respected senior members

Can anyone tell about the method of fixation of pay, when a state govt. official (Police Head Constable) is deputed to central govt. post (equivalent post Junior Intelligent Officer Gr-II in Intelligence Bureu).

for ex: An official drawing pay of Rs.9750 on 01.05.09 in the state govt. scale of Rs.6250-12000 (6250-125-6500-150-7100-175-7800-
200-8600-225-9500-250-10500-300-12000) (as per Fifth State Pay Commission of Karnataka State Govt. scale w.e.f 01.07.05) for pre-revised scale of 3300-75-3450-100-4450-125-5700-150-6300 , had assumed the equivalent post in the central govt. post having Grade pay of Rs.2400 in PB-1 pay 5200-20200+GP2400

Kindly intimate the pay to be fixed in the deputed post if the official opts to fix pay in the deputation post quoting relevant rules if any.