The vacuum tube is then known as a triode, tetrode, pentode, etc. The 7199 is a vacuum tube, combining a pentode and triode. The beam tetrode design of the 6L6 allowed RCA to circumvent Philips' pentode patent. The pentode is closely related to the beam tetrode. The pentode preamp tube is a 5879 with EL84 output tubes. The EL34 is a thermionic valve or vacuum tube of the power pentode type. The EL84 is a thermionic valve of the power pentode type. IF amplifier and a high slope output pentode. It used a single pentode vacuum tube and could register only twofold coincidences. This three-grid tube is called a pentode, meaning five electrodes. A pentode is an electronic device having five active electrodes. This tube was called the pentode. The Colossus computer and the Manchester Baby used large numbers of EF36 pentode tubes. In 1928 the company introduced the first pentode valve to the British market. Their design had the following features (compared to the normal pentode).