A lidar, which includes a transmitter and a receiver, as well as an optical system, which is arranged to direct at least part of the light sent by the transmitter as a transmitter beam progressing towards an object and to define the receiver beam to the receiver, at least part of the light arriving from the zone of which is focussed on the receiver. A portion of cooling air generated by the cooling fan is introduced into the muffler accommodating chamber so as to cool the muffler. The conduit includes a stabilizer with sensors to obtain data from the wellbore. A collector router issues a novel control message to a responder router over a default responder port. The private network is connected to an external data network such as the Internet, and has separate outbound resource servers to provide a high degree of scalability for handling a variety of message types. The end-ring includes an annular channel configured to catch the fluid flowing from the windings to the rotor and divert the fluid away from the air gap as the fluid flows from the rotor back to the stator, thereby limiting spin losses in the electric motor.