Mullard Cold Cathode
Indicator Tubes

Abbreviations: dp = decimal point, LH = left hand, RH = right hand.
Char. = character, Rec. = recommended, Maint = maintenance. HT = High Tension (ie., B+)

Mullard Type No.
Bulb colour

Char. Height /mm Min. HT /V

Maint. Voltage

Rec. Cathode Current /mA
Base & view
ZM1020 red 0123456789  15.5  170  140  2.0 B13B
end view
ZM1022 clear
ZM1021 red A V Ω + - % ~
ZM1023 clear
ZM1024 red c/s kc/s Mc/s ns μs ms s
ZM1026 red ½          
ZM1040 red 0123456789  30  170  140  4.0 B13B
side view
ZM1041 red - +  20
ZM1080 red 0123456789  13  170  140  2.0 Wire ended.
Side view.
ZM1082 clear
ZM1081 red - + ~  10.5
ZM1083 clear
(rectangular bulb)
  0123456789  15.5  170  140  2.0 14 pin special.
end view.
ZM1170 Red 0123456789  15.5  170  140  2.0 Wire ended.
Side view.
ZM1172 Clear
ZM1174 Red 0123456789
LH dp
ZM1175 Clear
ZM1176 Red 0123456789
RH dp
ZM1177 Clear
ZM1230 Red 0123456789  15.5  170  140  2.0 Wire ended.
Inverted side view.
ZM1232 Clear

ZM1080 Data (Mullard data sheet December 1968)

Limiting Values (Absolute)
Cathode current
(each digit).
Max average:
(Max averaging time = 20 ms)
3.5 mA
Max. Peak 12 mA
Min. average during conduction: 1.5 mA
Bulb Temp: Max: +70 °C
Min (see note 2) -50 °C


Pulse Operation
Max cathode current Peak: 12 mA
Average (Averaging time = 20 ms): 2.5 mA
Min cathode current for satisfactory display, average 0.8 mA
Pulse duration Max 20 ms
Min 100 μs
Anode to cathode maintaining voltage: see graph

Extinction Requirements
Max anode to cathode voltage to ensure extinction: 115 V

Life Expectancy
(at recommended operating conditions and room temperature).
Continuous display of one digit (see note 1): >5000 hours
Sequentially changing the display from one digit to the next every 100 hours or less: >30 000 hours

ZM1080.  Click for more views

Mounting Position:
The numbers are viewed through the side of the envelope. The numbers will appear upright (within ±3°) when the tube is mounted vertically.

Operating Notes:

1) The life expectancy figures given above relate to operation with DC cathode currents between 1.5 and 2.5 mA and at all permitted pulsed cathode currents. When a DC cathode current range of 1.5 to 3.5 mA is used, the life expectancy exceeds 3000 hours with continuous display of one digit.

2) For bulb temperatures below 0°C, the life expectancy of the tube is substantially reduced.

3) The leads are tinned and may be dip-soldered to a minimum of 5mm from the seals at a solder temperature of 240°C for a maximum of 10 seconds.

4) Care should be taken not to bend the leads nearer than 1.5mm from the seals.

5) The tube may be soldered directly into the circuit but heat conducted to the glass-to-metal seals should be kept to a minimum by the use of a thermal shunt.

Information on the use of pin 4 (primer pin)

ZM1080 Dimensions and pinout.

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