Abstract: A training instrument for use in teaching a trainee the proper use of a radioactivity measuring instrument includes a transmitter unit that is held and controlled by an instructor and further includes a receiver unit which is held and operated by the student and which simulates the radioactivity measuring instrument. The instructor selects a level of radioactivity to be measured by the student at a remote site, and that information is transmitted to the receiver unit in a moduated form that is not affected by atmospheric conditions or reflections from surrounding objects. Both the receiver and the transmitter include circuits that simulate the operation of a multirange meter. These circuits employ the most significant bits of a digital representation of the signal to determine which scale should be used, while the remaining digits indicate the magnitude of the signal as read on the selected scale.