Monitoring system for monitoring a kinematic chain comprising a support, a primary shaft mounted on the support so as to pivot about a first axis, a secondary shaft mounted on the support so as to pivot about a second axis and at least one transmission connecting the primary shaft to the secondary shaft, the monitoring system comprising: - at least one first sensor configured to supply at least one of first signals (41; 43) representing at least the speed and direction of rotation of the primary shaft, - at least one second sensor configured to supply at least one of second signals (42; 44) representing at least the speed and direction of rotation of the secondary shaft, - a first monitoring unit configured to acquire at least two of the first and second signals (41, 42; 44), configured to calculate the angular positions of the primary and secondary shafts and compare the positions, speeds and directions of rotation of the primary and secondary shafts with predetermined correct operation criteria and configured to operate at least one first output in a safe state if the correct operation criteria are not met, - a second monitoring unit configured to acquire at least two of the first and second signals (42, 41; 43), configured to calculate the angular positions of the primary and secondary shafts and compare the positions and speeds of rotation of the primary and secondary shafts with the predetermined correct operation criteria and configured to operate at least one second output in a safe state if the correct operation criteria are not met, - an output circuit, configured to acquire said first and second outputs and to operate at least one third output in a fail safe state if at least one of the first and second outputs (51, 52) is in a safe state, so that the kinematic chain can be placed in a safe state if a malfunction of the transmission has been detected. - at least one first sensor configured to supply at least one of first signals (41; 43) representing at least the speed and direction of rotation of the primary shaft, - at least one second sensor configured to supply at least one of second signals (42; 44) representing at least the speed and direction of rotation of the secondary shaft, - a first monitoring unit configured to acquire at least two of the first and second signals (41, 42; 44), configured to calculate the angular positions of the primary and secondary shafts and compare the positions, speeds and directions of rotation of the primary and secondary shafts with predetermined correct operation criteria and configured to operate at least one first output in a safe state if the correct operation criteria are not met, - a second monitoring unit configured to acquire at least two of the first and second signals (42, 41; 43), configured to calculate the angular positions of the primary and secondary shafts and compare the positions and speeds of rotation of the primary and secondary shafts with the predetermined correct operation criteria and configured to operate at least one second output in a safe state if the correct operation criteria are not met, - an output circuit, configured to acquire said first and second outputs and to operate at least one third output in a fail safe state if at least one of the first and second outputs (51, 52) is in a safe state, so that the kinematic chain can be placed in a safe state if a malfunction of the transmission has been detected.