Device included in a distance meter system

An improved optical electronic distance measuring system including an operator positioned optical reflector and a transmitter/receiver for transmitting electromagnetic radiation in the visible or infrared wavelength region, modulated by a continuous periodic measuring signal, towards said optical reflector and for receiving modulated radiation reflected by said optical reflector, said transmitter/receiver further including distance circuit means for deriving a distance measurement, representative of the distance between said transmitter/receiver and said optical reflector, from a phase difference between said measuring signals modulated onto said transmitted and received radiation, characterized in that:

• said transmitter/receiver includes first modulator means (14, 27) with a first input connected to a source of an audible information signal (10, 11 or 7-9) and a second input connected to a source of said continuous periodic measuring signal, said modulator means modulating said audible information signal from said source onto said continuous periodic measuring signal,
• said transmitter/receiver further includes filter means (5) to filter said audible information signal from a received signal produced from said received radiation before said received signal is coupled to said distance circuit means, and
• an optical receiver (16-20) located adjacent said optical reflector (2) for responding to said transmitted radiation, said optical receiver including an optical or infrared detector (15) and demodulator circuit means (19) for demodulating an audible signal from said transmitted radiation,
• wherein said source of an audible information signal includes means for giving an audio frequency signal having a clearly perceivable, continuous difference for different signal strengths of said radiation received by said transmitter/receiver, and that said audio frequency signal either directly via an inner path in said transmitter/receiver or via a loudspeaker and a microphone is modulated on said measuring signal.