Model 4122B is a 19-inch wide by 1 3/4-inch high, rack mountable, line powered current source power unit and voltage gain amplifier, designed to power up to 6 channels of IEPE sensors. Model 4122B supplies power to operate the sensors' built-in amplifiers, decouples the signal from the sensors' DC bias and provides voltage gain to the sensor signal for each channel, individually, in switch-selected steps of x1, x10 and x100. It can power up to 6 channels simultaneously. The front panel of the unit contains a single BNC output jack for monitoring the sensor signal at the input of any channel with a single readout instrument, such as an oscilloscope. The selection for this purpose is made by a 6 position rotary switch which is also used to select a channel for fault monitoring. The front panel of model 4122B contains: The power on/off toggle switch;The power "on" indicator lamp;The fault monitor voltmeter to check for normal sensor and cables;A 6-position rotary selector switch to select the channel for fault monitoring and for input signal monitoring;A BNC jack labeled "monitor" to allow monitoring of the input signal to the gain amplifiers from the sensor;6 3-position toggle switches to set the voltage gain individually for each channel;6 BNC output jacks carrying the amplifier output signal for each channel. The back panel of model 4122B contains The AC power cord (3-wire, 6-feet long);A fuse holder for the replaceable fuse;6 "Sensor" BNC jacks for connection to the IEPE sensors;6 BNC "Output" jacks carrying the amplified signal from each channel (the rear panel jacks are duplicates of the front panel output jacks and are connected electrically in parallel with them)