Abstract: The invention pertains to a drilling fluid composition comprising:—at least one (per)fluoropolyether oil comprising recurring units of formula —CF(CF3)CF2O— said oil having a kinematic viscosity of 30 to 80 cSt measured according to ASTM D455 standard at 20° C. [oil (E)] and possessing a polydispersity index (PDI) of at least 1.15; and—at least one (per)fluoropolyether phosphate comprising at least one perfluoropolyoxyalkylenic chain and at least one phosphoric acid group, in its acid, amide, salt or ester form [phosphate (P)], to a method for its manufacture and to its use in a drilling rig equipment.

Abstract: A method for testing a digital data transmission line connected between two modems, including the steps of transmitting a test message from the first modem to the second modem, comparing the received message with the standard test message to determine errors, transmitting a test message back to the first modem along with the error message determined from comparing the received test message with the standard test message at the first modem. The error signal transmitted to the first modem and the error detected there is interpreted to determine the error in the transmission.