Twin Electro-Magnetic Telemetry Systems are for high-speed EM MWD/LWD.
As alternatives or supplements to mud pulse telemetry, they transmit drilling data, to enable use of mud pulse and EM telemetry concurrently. This provides quicker EM data transmission with full redundancy.
Twin EM encodes downhole MWD data into low-frequency EM waves. The signal is transmitted from the tool through the formation and detected on the surface.