1 - History of Ericsson - History of Ericsson

NGC 303
NGC 313
NGC 323
NGC 343
Fig. 4 X 2755—2759
Different types of rare gas tube
36
seconds the average residual voltage affords a level of protection of some
500 V, at which no damage can be incurred during so short a time. This
result has been measured both with an oscillograph and with a specially constructed
electronic, highly rapid peak-voltage meter which gives an indication of
longer duration.
The electrodes, as noted, are bimetallic strips. During relatively lengthy
discharges, which occur on permanent contact with power lines, the bimetallic
strips are heated and come together to produce a short-circuit. On a powerful
arc discharge through the tube the short-circuit is effected after about 0.5
second. It persists during the period of the disturbance and for a few seconds
thereafter. The short-circuit also protects the cathode layers against gasification
and greatly increases their life.
Data
Static striking voltage: Standard values are 250. 300, 350 and 400 V DC.
Shock striking voltages with wave form 1/50: (on tubes for up to 600 V DC
static striking voltages) < 1,000 V.
Maintaining voltage on glow discharge: 75-150 V DC.
Maintaining voltage on arc discharge: 15-30 V DC (at > 100 mA).
Insulation: > 5,000 Mohms.
Time of arc hejore electrodes are short-circuited: 2-4 seconds at 5 A, 0.5-1.5
second at 20 A.
Electrode breaking time: after 5-10 seconds.
Rupture limit of glass base after 1-minute continuous current: > 20 A.
Rupture limit of glass base at 1.5 Coulomb: > 2,000 A.
Continuous current load (unlimited time): 15 A.
Cathode activation: Withstands current loads up to rupture limit of glass base.
The electrode system in NGC 31 is used in several other types of tubes for
2-pole and 3-pole termination as shown in fig. 4. All these tubes are valuable
and robust components in telephone networks.
Further information concerning the various types of tubes, their dimensions,
electrical data, holders, etc. will be found in "News from the Network Department"
No. N 16e: Rare Gas Tubes.