Altek Model 334A Loop Calibrator has been designed to check, calibrate, and troubleshoot all the signals present within a standard 4 to 20 milliamp process control loop. A 24 mA source, mA meter, Two wire transmitter simulator, and a DC volt meter are combined into one easy-to-operate instrument. Dual current ranges allow display of each current function in percent of 4 to 20 mA signal, as well as directly in milliamps. Power and measure two wire transmitters simultaneously in Source Mode. The Altek model 334A supplies the required voltage and displays the current as regulated by the 2-wire transmitter. The Model 334A may also be used when a controller is temporarily removed for repair or replacement. Simply substitute the Model 334A for the controller and use it as a manual loading station. Bench-top accuracy in a toolbox calibrator assures fast, precise setting of current trips, recorders, controllers, loggers, computers, and final control elements.