Your TR-440 is a portable, single channel analog recording system complete with amplifier. The TR-440 uses a fully transistorized d.c. amplifier and records data in the frequency range of d.c. to 100 cps with a heated stylus and a heat sensitive chart. It has a calibrated measurement range from 50 millivolts to 400 volts; uncalibrated, the range is 10 millivolts/mm to 50 millivolts/mm. The TR-440 may be used to record physical data — weight, force, pressure, temperature, rotation, light intensity — as well as countless electrical signals. These electrical or physical ‘variables” may be either varying or constant. A physical phenomenon may be measured by a pressure transducer, for example. The pressure transducer converts the physical change into proportional voltage which is an “analog” to the change in pressure. This change is amplified and is then permanently recorded on a moving, precision-engineered chart. The TR-440 accepts, in lieu of a physical change, an electrical value which represents the physical change.