{"product_id":"antique-induction-spark-gap-ruhmkorff-coil-with-rule-measure","title":"Antique Induction \/ Spark Gap \/ Ruhmkorff Coil With Rule Measure","description":"\u003ch1\u003eAntique Induction \/ Spark Gap\/ Ruhmkorff Coil With Rule Measure\u003c\/h1\u003e\n\u003cp\u003eThis is a quite rare British Antique Induction \/ Spark Gap \/ Ruhmkorff Coil With Rule Measure, possibly made for the GPO.  A great find for all collectors of vintage technology and early radio \/ telegraphy aficionados.\u003c\/p\u003e\n\u003cp\u003eThe top of the wood base has the following labels and a a white bakelite rule labelled 0-50 which, I think ..., measures the spark length which is linearly proportional to the voltage:\u003c\/p\u003e\n\u003cul class=\"KsbFXc U6u95\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 400; margin: 12px 0px 16px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003e\n\u003cli class=\"Z1qcYe\" data-sfc-cp=\"\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-hveid=\"CAIIAAgBCAUQAA\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 400; margin: 0px 0px 12px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003e\u003cspan class=\"T286Pc\" data-sfc-cp=\"\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 400; margin: 0px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003e\u003cstrong class=\"Yjhzub\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 700; margin: 0px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003eB (Battery):\u003c\/strong\u003e The terminal that connects to the positive side of the DC power source or battery, providing the initial voltage.\u003c\/span\u003e\u003c\/li\u003e\n\u003cli class=\"Z1qcYe\" data-sfc-cp=\"\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-hveid=\"CAIIAAgBCAUQAQ\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 400; margin: 0px 0px 12px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003e\u003cspan class=\"T286Pc\" data-sfc-cp=\"\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 400; margin: 0px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003e\u003cstrong class=\"Yjhzub\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 700; margin: 0px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003eP (Primary):\u003c\/strong\u003e The terminal connected to the primary coil circuit. On classic induction coils, this connects to the interrupter (vibrator) which rapidly opens and closes the circuit.\u003c\/span\u003e\u003c\/li\u003e\n\u003cli class=\"Z1qcYe\" data-sfc-cp=\"\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-hveid=\"CAIIAAgBCAUQAg\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 400; margin: 0px 0px 12px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003e\n\u003cspan class=\"T286Pc\" data-sfc-cp=\"\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 400; margin: 0px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003e\u003cstrong class=\"Yjhzub\" data-sfc-root=\"ep\" data-sfc-cb=\"\" data-complete=\"true\" data-copy-service-computed-style='font-family: \"Google Sans\", Arial, sans-serif; font-size: 16px; font-weight: 700; margin: 0px; text-decoration: none; border-bottom: 0px rgb(10, 10, 10);'\u003eS (Secondary):\u003c\/strong\u003e The terminal connected to the very fine wire of the secondary winding, which outputs the final high-voltage spark.\u003c\/span\u003e\u003cspan\u003e \u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eApproximate Size:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eWidth: 15.2 cm (6\")\u003c\/li\u003e\n\u003cli\u003eHeight: 5 cm\u003c\/li\u003e\n\u003cli\u003eDepth: 8.9cm\u003cbr\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThe wood plinth and components are in fairly good condition with scratches, scuffs, and blemishes commensurate with age and use. \u003cspan style=\"color: rgb(255, 42, 0);\"\u003eIt is being sold as a collectible, for display only, and has not been tested.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cmeta charset=\"utf-8\"\u003eInduction coil or \u003cem\u003espark coils\u003c\/em\u003e were used in early radio signalling testing, (see attached schematic), however the function of this induction coil was possibly not so benign. Shock Therapy was used extensively in Victorian and Edwardian times as a Quack cure, or at least as a therapeutic device, for a multitude of complaints and illnesses. We think this device dates to the Edwardian period: early 20th Century.\u003c\/p\u003e\n\u003cp\u003eThis particular device is portable, being quite small. It would have been powered from a battery-not included.\u003cstrong\u003e\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eAccessories shown in one of the images are for illustration only and are not included.\u003c\/p\u003e\n\u003cp\u003ePlease click on the following links for more \u003ca rel=\"noopener noreferrer\" href=\"https:\/\/mullardantiques.co.uk\/collections\/vintage-technology-scientific-engineering-imaging-medical-equipment-instruments-tools\" target=\"_blank\"\u003evintage technology\u003c\/a\u003e and \u003ca rel=\"noopener noreferrer\" href=\"https:\/\/mullardantiques.co.uk\/collections\/vintage-medical-devices\" target=\"_blank\"\u003emedical related ephemera.\u003c\/a\u003e\u003c\/p\u003e\n\u003ch2\u003eSpark Gap Transmitter and Induction Coils\u003c\/h2\u003e\n\u003cp\u003eA spark-gap transmitter is a device that generates radio frequency electromagnetic waves using a spark gap. This was the technology used in the first thirty years of radio transmission (1887- 1920s), using morse code, prior to the introduction of radio valves\/ vacuum tubes. In order to create a spark gap you need an induction\/ spark coil, (also known as an inductorium or Ruhmkorff coil after the inventor, Heinrich Rumhkorff), which produces high voltage pulses from low voltage DC.\u003c\/p\u003e\n\u003cul\u003e\u003c\/ul\u003e\n\u003cp\u003ePlease click on the following link for more \u003ca href=\"https:\/\/mullardantiques.co.uk\/collections\/vintage-technology-scientific-engineering-imaging-medical-equipment-instruments-tools\" target=\"_blank\"\u003evintage technology.\u003c\/a\u003e\u003cspan class=\"theme-text-color-0-0\"\u003e\u003cu\u003e\u003cstrong\u003e\u003c\/strong\u003e\u003c\/u\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan style=\"border-top-left-radius: 2px; border-top-right-radius: 2px; border-bottom-right-radius: 2px; border-bottom-left-radius: 2px; text-indent: 20px; width: auto; padding: 0px 4px 0px 0px; text-align: center; font-style: normal; font-variant-caps: normal; font-weight: bold; font-stretch: normal; font-size: 11px; 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