operation of the upper esp 24 u whilst the lower esp 24 l remains dormant position 2 of the switch arm 38 is shown in fig4 c where the switch arm 38 has been moved by the piston 32 via the mechanical coupling 36 such that the three phases a b and c of the electric cable 14 are now electrically coupled to the three phases g h and i of the lower esp 24 l accordingly position 2 provides full power to and operation of the lower esp 24 l whilst the upper esp 24 u becomes dormant consequently the operator can from the surface select which of the two esps 24 bl 24 bu to operate by actuating the hydraulic switch 24 b with surface control equipment to move the piston 32 against the return spring 33 to move the switch arm 38 to the desired position 1 or 2 all the while only having to run one electric cable from the surface down to the dual esps 24 bu 24 bl the operator can lock the pressure in the hydraulic fluid at the surface to hold the position 1 or 2 of the switch arm 38 an alternative lower half of the completion 9 c is shown in fig3 c where the lower esp 24 cl constitutes the lowermost portion of the completion 9 c and its output feeds straight into the lowermost end of the production tubing 18 as can be seen in fig3 c the upper esp 24 cu and the switch 26 c are arranged in a similar manner to the upper esp 24 bu and the switch 26 b of the system 9 b of fig3 b a.