Abstract: To monitor the rotation speed and torque transmitted by a shaft (120) in order to determine the power transmitted by the shaft (120). To achieve this torque sensing means 124 and rotation speed sensing means (103) are provided, each connected to an interface means (104). Signals are transmitted between said torque sensing means (124) and said interface means (104) by way of a coupling arrangement comprising a first coupling element (121) is fixed to and co-rotates with shaft (120) and a second coupling element (102) is fixed to a stator (101) surrounding said shaft (120) and thus remains stationary whilst shaft (120) rotates. The first coupling element (121) is in the form of a split ring having a ring gap (127) and is electrically connected to the torque sensing means (124). The first coupling element (121) has a comb-like form wherein the ring provides a spine upon which are formed a plurality of teeth (122), which project from said spine.