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"Radio Engineering" for December 1927 reviewed this tube and states:
"The Shieldplate Tube Corporation, 206 La Salle Street, Chicago Ilinois announce a new four element tube known as the SP122. This tube employs a screen grid which entiely surrounds the plate of the tube, both inside and outside. The grid acts as a shield between the plate and the control grid, thereby reducing the capacity betwen the two elements to a negligable quantity.
"Due to this arrangement the tube has an amplification constant of 175, it is stated.
"The tube is designed primarily for use as a radio frequency amplifier but can be used as a detector or an audio frequency amplifier with a few changes to the circuit connections.
"The filament voltage of the tube is 3.8 volts and the filament consumption is .133 ampere. Due to the low filament consumption it can be operated from dry cells or if desirable, from a 6 volt storage battery, by using a 15ohm fixed resistance in series with the negative filament lead.
"Much greater amplification can be obtained from this tube in both radio and audio frequency circuits.
Offered by "Shieldplate Tube Corporation ", 4053 Diversey Ave., Chicago, Illinoiis as "Shielldplate Tube SP11 AC Shielded Grid Amplifier. Tubes are the latest development in radio..." (Call Book November 1928? Dale Davenport for a custom built Tyrman Imperial 80 superhet),
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