Manual of Wireless Telegraphy, Manhattan Electrical Supply Company, Number nine (1916), page 109:
Type "T" Audion Bulb
The Audion Detector is the most sensitive and reliable in existence.
For the benefit of those amateurs who desire to experiment, and who do not wish to buy complete Audion Detectors with the necessary accessories, and for those whose limited means will not permit the complete instruments to be purchased, we have brought out the Type T Tubular Audion Bulb.
It is licensed for amateur use only and is NOT interchangeable with the regular round Audion Bulbs.
This type of Audion Bulb gives very loud response to signals.
The life of the Type T Tubular Bulb is exceptionally long on account of the fact that the single straightline filament has no loops, and as there is no second filament, the Edison discharge to same is completely eliminated.
The plate or wing is in contact with the glass, preventing overheating. The filament is surrounded by a spiral grid.
This type of bulb is an excellent oscillator for the reception of continuous waves, being different in this respect than round Audion Detector Bulbs.
The grid is the spiral inside the tube and is connected to the green covered wire. The plate is connected to the red covered wire. The filament terminals are the white covered wires. This type of Audion Bulb is the only one sold separately.
8444 Type "T" Audion Bulb
Miniature Battery Rheostat
Suitable for regulating the voltage of battery circuits in connection with miniature lamps, small motors, etc.
The change in resistance is gradual as the lever passes over the coiled resistance wire, from 0 to 10 ohms. When resting on "off" the circuit is open. In any other position the circuit is closed.
Binding posts and lever nickel plated. Porcelain base. Diameter, 37/8 in.
Used in connection with De Forrest Audion. The composition of the resistance wire renders it extremely tough so that breakage is eliminated.
Maximum resistance is 10 ohms. Not recommended for use with any device consuming more than 1½ amperes of current.
Experimentalists, physicians, surgeons, workers in laboratories, etc., will find this a very useful and efficient miniature rheostat.
2110 Miniature Battery Rheostat
Directions for Using the Type "T" Tubular Audion Bulb
1. The diagram below illustrates the various accessories needed with the bulb. Our No. 2110 Battery Rheostat is used. Battery B consists of 10 three cell flashlight batteries, each showing at least 3½ volts on a voltmeter. They are connected in series, with zinc of one to carbon of the next, and so on throughout the series. It is very important that each shows at least 3½ volts to 4½ volts and that they are properly connected together, otherwise the results will be very poor. The negative or zinc end of this battery must lead to the filament.
A switch is to be arranged as shown to cut in 6, 7, 8, 9 or 10 batteries at will.
Fixed condenser No. (F.C.) consists of two sheets of tin foil 2 inches square, separated by a mica sheet. This must be of first-class construction, and of small capacity. A small variable condenser may be substituted.
Battery A should be a 6 volt storage battery of at least 40 Ampere hours capacity. Two sets of dry cells, each having 4 cells may be arranged in parallel instead, but the storage battery is recommended.
Do not permit either of the filament wires to come in contact with any circuit or any metal part carrying current. This might connect it to the Battery B and burn out the filament.
No credit can be offered for a bulb burned out from any cause.
2. The bulb must be operated in a vertical position to give best service.
3. Always turn in all resistance on the rheostat before lighting the filament. Batteries recuperate on standing idle and the increase of voltage might burn out the filament.
4. Adjust rheostat to give normal filament brilliancy and adjust Battery B switch to best point. Then try reversing current from the lighting battery to find out which direction is better.
5. The bulb is most sensitive at a point just below that at which the hissing sound is heard in the telephones.
6. The receivers should be each of at least 1,000 ohms resistance.
7. FOLLOW THESE DIRECTIONS TO THE LETTER. They are important.