A Single Ended Push–Pull (SEPP, SRPP or mu-follower) output stage, originally called the Series-Balanced amplifier (US patent 2,310,342, Feb 1943). is similar to a totem-pole arrangement for transistors in that two devices are in series between the power supply rails, but the input drive goes "only to one of the devices," the bottom one of the pair; hence the (seemingly contradictory) Single-Ended description. The output is taken from the cathode of the top (not directly driven) device, which acts part way between a constant current source and a cathode follower but receiving some drive from the plate (anode) circuit of the bottom device. The drive to each tube therefore might not be equal, but the circuit tends to keep the current through the bottom device somewhat constant throughout the signal, increasing the power gain and reducing distortion compared with a true single-tube single-ended output stage.