Peanut 215, which instead of using prongs had a tiny bayonet base with four drop-like contacts. Another exception is the European Side Contact series commonly known as P, which instead of using a prong, relied on side contacts at 90 degrees from the tube axis with four to twelve contacts. Octal In April 1935, the General Electric Company introduced a new eight-pin tube base with their new metal envelope tubes. The new base became known as the octal base. The octal base provided one more conductor with a smaller overall size of the base than the previous line of U. S. tube bases which had provided a maximum of seven conductors. Octal bases, as defined in IEC 60067, diagram IEC 67-I-5a, have a 45-degree angle between pins, which form a diameter circle around a diameter keyed post (sometimes called a spigot) in the center. Octal sockets were designed to accept octal tubes, the rib in the keyed post fitting an indexing slot in the socket so the tube could only be inserted in one orientation. When used on metal tubes, pin 1 was always reserved for a connection to the metal shell, which was usually grounded for shielding purposes. This reservation prevented tubes such as the 6SL7/6SN7 dual triodes from being issued with metal envelopes, as such valves need three connections (cathode, grid, anode) for each triode (making six total) plus two connections for the paralleled heaters. The octal base soon caught on for glass tubes, where the large central post could also house and protect the "evacuation tip" of the glass tube. The eight available pins allowed more complex tubes than before, such as dual triodes, to be constructed. The glass envelope of an octal base tube was cemented into a bakelite or plastic base with a hollow post in the center, surrounded by eight metal pins. The wire leads from the tube were soldered into the pins, and the evacuation tip was protected inside the post. Matching plugs were also manufactured that let tube sockets be used as eight-pin electrical connectors; bases from a discarded tubes could be salvaged for this purpose. Octal sockets were used to mount other components, particularly electrolytic capacitor assemblies and electrical relays; octal-mount relays are still common. Most octal tubes following the widespread European designation system have penultimate digit "3" as in ECC34 (full details in the Mullard–Philips tube designation article). There is