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Specialized - Switching Tube ·RelayControlSwitch

451A

Four-electrode inert-gas-filled cold-cathode relay tube with isolated starter and main gaps, providing controlled gas-discharge switching with isolation between control and load circuits.

Directly heatedCold cathodeCommon cathodeDissimilarSpecialized
Sections
1
Base
-
Socket code
UX4
Base pins
9
Nominal heater
-

Description

The 451A is a four-electrode inert-gas-filled cold-cathode relay tube with an anode-cathode gap and a starter anode-starter cathode gap, providing isolation between control and controlled portions of a circuit.

Socket description

Medium-shell UX 4-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
UX4
Base pins
9
Nominal heater voltage
-
Nominal heater current
-
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

RelayControlSwitch

X-ray radiationInterelectrode capacitances
Max cathode current
50 mA

Main anode-cathode gap plus starter anode-starter cathode gap; peak main cathode current 50 mA, average 20 mA.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

2026 Western Electric 400s

Published operating points and test conditions from this source.

SECTION 1

RelayControlSwitch

Other

  • Peak Anode Voltage Forward or Inverse

    - to 180 V

  • Peak Cathode Voltage to Other Electrodes

    - to 180 V

  • Average Main Cathode Current

    - to 20 mA

    2-second averaging

  • Peak Starter Cathode Current

    - to 7 mA

  • Average Starter Cathode Current

    - to 2.5 mA

    2-second averaging

Characteristic

  • Starter Breakdown Voltage

    67 to 90 V

  • Starter Voltage Drop at 2.5 mA

    55 to 75 V

  • Anode Voltage Drop at 10 mA

    58 to 80 V

  • Ionization Time Starter Gap

    5 ms

    Approximate

  • Deionization Time Main Gap

    1 ms

    Approximate