dʒˈɛnɚɹəli, ˈɑːd nˈʌmbɚz aɪdˈɛntᵻfˌaɪd tˈuːbz slˈæʃ vˈælvz wɪð vˈɛɹɪəbəl mˈuː kˌæɹɪktɚɹˈɪstɪks ænd ˈiːvən nˈʌmbɚz stɹˈeɪt, ɔːɹ ʃˈɑːɹp kˈʌtˈɔf tˈaɪps.
Generally, odd numbers identified tubes / valves with variable mu characteristics and even numbers straight, or sharp cut-off types.