From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Advertisement for the 'POL' permanent, self-resetting mercury fuse.
| Identifier | ExFiles\Box 166\7\ img056 | |
| Date | 3rd November 1936 guessed | |
| THE FUSE WITHOUT COMPARE -YOU NEVER NEED A SPARE! Fit a “ POL ” permanent mercury fuse and you will never be stranded with a burnt-out fuse. A column of mercury takes the place of the usual fuse wire inside the brass-capped glass tube. When the fuse breaks, due to “ shorting ” or overloading of the circuit, a gap is caused in the thin mercury column. This is simply rejoined by tapping one end on hard surface until column is completed, and immediately the fuse is as good as new again. The efficiency of the fuse is not impaired by repeated breaking and rejoining of the mercury thread. Hence the name “ POL ” Permanent Fuse. There is another big advantage in using a “ POL ” Mercury Fuse which many fuse manufacturers have hitherto sought to obtain, namely—TIME LAG. The normal wire fuse, when loaded above its carrying capacity, burns-out in approximately 60 secs. The “ POL ” Mercury Fuse, however, resists slight short circuits and small overloads for a period of 10-15 mins., so that a loose flapping wire, causing a momentary “ short,” will not blow the fuse and plunge the driver in darkness. With a definite short circuit or overload the “ POL ” fuse breaks at once, but is not permanently destroyed—a tap renews the column immediately. Manufactured in the following amperages: 4.5, 5, 6, 8, 10, 15, 20, 25, 30, 35, 40 amps. Exclusive Wholesale Distributors S. GUITERMAN & CO. LTD. 35 & 36 ALDERMANBURY, LONDON, E.C.2 Telephone : METROPOLITAN 8074 (3 lines) Telegrams : GUITERMAN, PHONE, LONDON RETAIL PRICE 1/6 EACH A TAP RENEWS THE BURNT-OUT FUSE [Text on packaging display] POL PERMANENT FUSES 1/6 15 AMP 5 AMP 10 AMP 20 AMP VICKERS PAT [Text on single fuse illustration] POL Permanent fuses 30 AMP | ||