{"product_id":"vintage-sel-induction-coil-no-1700-spark-gap-generator","title":"Vintage SEL Induction Coil No. 1700. Spark Gap Generator","description":"\u003ch1\u003eVintage SEL Induction Coil No. 1700. Spark Gap Generator\u003c\/h1\u003e\n\u003cp\u003eThis is a quite rare British Vintage SEL Induction Coil No. 1700. Spark Gap Generator \/ Transmitter. A great find for all collectors of vintage technology.\u003c\/p\u003e\n\u003cp\u003eIn very good condition, it comes in its original brown SEL branded cardboard box with instruction leaflet (part of which is missing).\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eApproximate measurements:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eBase Width: 8.8 cm\u003c\/li\u003e\n\u003cli\u003eBase Length:- 10.1 cm (4\")\u003c\/li\u003e\n\u003cli\u003eHeight: 6 cm\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThis small induction coil was made by Signalling Equipment Limited (SEL) under their Merit brand: catalogue number 1700.  The base is made from blue plastic and the mounted coil is wrapped in green foil with the Merit brand logo; they are in excellent condition.\u003c\/p\u003e\n\u003cp\u003eInduction coil or \u003cem\u003espark coils\u003c\/em\u003e were used in early radio signalling testing, however, the function of this induction coil was probably not so benign. It was actually sold as a toy, and probably used by the owner to give their unwitting pets, friends and relatives electric shocks! Needless to say that this sort of 'toy' is no longer available! This version dates to the 1950s\/60s.\u003c\/p\u003e\n\u003cp\u003e\u003cspan style=\"color: #ff2a00;\"\u003eWe are selling this induction coil as a scientific curio and have deemed it unsuitable for use by children.\u003c\/span\u003e \u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eSummary\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eRadius cornered blue plastic base, induction coil with output wired to two metal cylinders\u003c\/li\u003e\n\u003cli\u003eRequires a 4.5 volt battery (not included). Not for mains use.\u003c\/li\u003e\n\u003cli\u003eManufacturer SEL (Trade name for \u003cspan data-mce-fragment=\"1\"\u003eJ. C. L. Randall of Potters Bar, Middlesex)\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003eMarked on the Box with\u003c\/li\u003e\n\u003cul\u003e\n\u003cli\u003eSEL (Signalling Equipment Limited)\u003c\/li\u003e\n\u003cli\u003eInduction Coil\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/ul\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\u003c\/p\u003e\n\u003cdiv data-element-id=\"id1429604210185\" id=\"id1429604210185\" class=\"design-element element-size-box has-rich-content user-selectable-element clickable-element has-rich-content has-text is-section-child\"\u003e\n\u003cdiv data-element-id=\"id1429604210185\" class=\"element-main-box design-element-main-box has-rich-content user-selectable-element clickable-element has-rich-content has-text\"\u003e\n\u003cdiv data-element-id=\"id1429604210185\" class=\"element-border-box element-border-target element-padding-box design-element-border-box has-rich-content user-selectable-element clickable-element has-rich-content has-text\"\u003e\n\u003cdiv data-element-id=\"id1429604210185\" class=\"element-content-box design-element-content-box has-rich-content user-selectable-element clickable-element has-rich-content has-text\"\u003e\n\u003cdiv data-element-id=\"id1429604210185\" class=\"content-container content-container-type element-size-box element-size-target has-rich-content user-selectable-element clickable-element has-rich-content has-text\"\u003e\n\u003cdiv class=\"rich-text-element-content absolute-fill element-content dir-ltr\"\u003e\n\u003cdiv class=\"rich-text-positioning-wrapper vertical-alignment-top\"\u003e\n\u003cdiv class=\"rich-text-content common-rich-content-style has-content\"\u003e\n\u003cdiv\u003e\n\u003cdiv\u003e\u003cspan class=\"theme-text-color-0-0\"\u003e\u003cu\u003e\u003cstrong\u003e\u003c\/strong\u003e\u003c\/u\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cspan style=\"border-top-left-radius: 2px; 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