In 1933 the OSIRA lamp, discovered and developed by the G.E.C. Research Laboratories, was first put on the market. Since then these lamps have been steadily improved, and now the G.E.C. is able to announce a further development of its Research Laboratories, the new 80 and 125 Low Wattage High Pressure Mercury Vapour lamps.

The 80 and 125 watt OSIRA lamps are similar in shape to the 150 and 200 watt Pearl OSRAM filament lamps respectively, but differ externally in having a 3-pin bayonet cap. The purpose of this is to prevent the insertion of the lamp into a standard 2-pin B.C. lampholder, where a stabilising choke is not provided in circuit with it.

The new low wattage OSIRA lamps have a luminous efficiency much more in line with that of the high wattage sizes than is the case with the comparable wattage tungsten filament lamps. This is due to the higher temperature at which the discharge operates, necessitating the use of an inner quartz glass.

The OSIRA 125 watt PEARL FINISH lamp

TECHNICAL DATA Lamp Wattage 80 125 Standard Cap 3-pin B.C. 3-pin B.C. Initial Light Output In Lumens 3040 5000 Efficiency In Lumens Per Watt (Initial) 38 40 Average Life In Hours 1500 1500 Overall Length (Distance of cap contact to bottom of lamp) 160 +/- 4.5 m/m 178 +/- 5.5 m/m Diameter Of Outer Bulb 80 m/m 90 m/m Light Centre Length (distance of cap contact to middle of discharge) 120 +/- 4 m/m 133 +/ 5 m/m Length of Light Source 20 m/m 30 m/m VOLTAGE RANGE AND PRICES. Low wattage OSIRA lamps are available in two wattages and four voltage ranges to suit the actual voltages available at the units. Watts. Voltage Range. To be used withChoke, Cat. No. Price per lamp 80 200/210, 220 230, 240/250 Z 1820 Type B Z 1821 Type H £1 10s. 0d. £1 10 0 125 200/210, 220 230, 240/250 Z 1830 Type B Z 1831 Type H £1 15s. 0d. £1 15 0

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