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				HF tetrode 
				Introduced in 1927 
					
						
							| 1 | 2 | 3 | 4 | tc | base |  
							| g2 | f | f | g1 | a | B4 |    
					
						| Vf | Af | Va | Vs | Vg | mAa | mAs | ra | gm |  
						| 4 | 0.1 | 200 | 100 | -1 | 4.5 | 0.8 | 400,000 | 0.9 |  B442 serie 100 is for 
						series feed 
							
								| Equivalent | 1915, A2004, C150, 
								DZ2, 
								H410D, 
								L409, PM13X, R81, RES024, RES094, RO4142, 
							S406, S410, 
								TB42, VH300 |  |