On this diagram there are four blocks, 1 switch, 5 resistors, 1 capacitor, two pentode tubes, and an output transformer. The resistors, tubes, and transformer, are not permanent parts on the test bed. The four blocks are, the metering circuit, the screen voltage supply, cathode follower and bias, and the phase inverter. The switch is labeled HV switch. A terminal labeled external HV goes to one side of the HV switch, an S P S T. The other side of the switch connects to the plate milliammeter plus terminal and plate terminal of the voltmeter on the metering circuit block. The output of the screen voltage supply connects to the screen milliammeter plus terminal and screen terminal of the voltmeter on the metering circuit block. The plate milliammeter minus terminal connects to the center tap of the output transformer primary. The screen milliammeter minus connects to the screen grids of the output tubes. The cathode terminal on the voltmeter connects to the cathodes of the tubes. The grid 1 A terminal of the voltmeter connects to one of the outputs of the cathode follower driver and bias block. The grid 1 B terminal of the voltmeter connects to the other output of the cathode follower driver and bias block. There is a jack labeled signal in which feeds into the phase inverter block. On this diagram there is no connection to the two inputs of the cathode follower driver and bias block. Each output of the cathode follower driver and bias block goes to its own 470 k ohm resistor. The other end of each 470 k ohm resistor goes to its own 1 k ohm resistor. The other end of each 1 k ohm resistor goes to the control grid of one of the two pentode tubes. One of the outputs of the phase inverter goes to the junction of one of the 470 k ohm and 1 k ohm resistors. The other output of the phase inverter goes to the junction of the other 470 k and 1 k ohm. The cathodes of the tubes go to one end of the parallel combination of a resistor and capacitor. The other end of the parallel R and C connect to a point labeled output cathodes to relay contact. The screen grid connections have been described above. The suppressor grids are tied internally to the cathodes. The plate of each tube goes to one end of the output transformer primary. The secondary is not connected but would have a load on it.