{"product_id":"1920s-telegraph-gpo-standard-type-b-relay","title":"1920s Telegraph GPO Standard Type B relay","description":"\u003ch1 class=\"override-listing-title normal break-word mb-xs-2\" data-buy-box-listing-title=\"\" data-listing-id=\"682913823\"\u003e1920s Telegraph GPO Standard Type B relay\u003c\/h1\u003e\n\u003cp\u003eThis is an extremely rare 1920s Telegraph GPO (General Post Office) Standard Type B relay, and is usually only seen in telecommunications museums e.g. the museum of technology. This particular relay is unusual in that it has ‘Double throw contacts.’ It has not been tested.\u003c\/p\u003e\n\u003cp\u003eThe reference number on the relay is:-\u003cbr\u003eCrown mark\u003cbr\u003e2613\u003c\/p\u003e\n\u003cp\u003eEngraved with the words ‘Spacing Marking’\u003c\/p\u003e\n\u003cp\u003eThis particular telegraph relay is a work of great design and engineering, and is in fair condition. The price has been reduced to account for the level of cosmetic defects.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eBrass is pitted on the case and knobs (but may benefit from a careful polish)\u003c\/li\u003e\n\u003cli\u003eThere is a small crack in the glass lid\u003c\/li\u003e\n\u003cli\u003eThe wood varnish has mottled\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eEven if you aren’t a collector of early telegraph or communications equipment, you can’t failed to be impressed by the brass and wood design. It would look wonderful as a paperweight or a desk ornament. An interesting Gizmo or Gadget to talk about in the office!\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eApproximate Measurements:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eBase Diameter: 13.5cm\u003cbr\u003eHeight: 13cm\u003c\/p\u003e\n\u003ch2\u003e\u003cstrong\u003eWhat is it?\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp\u003eIn telegraphic communication, sound is transmitted as current via cables. Voltages and current are kept low in the cables for safety’s sake. If the cables are very long, the power has to be amplified in order to operate effectively (receive a signal) at the local telegraph station. On reaching the local station, the high resistance relay connects with the main cable. This results in an electrical contact within the relay, which is then passed in the local circuit to a battery and ‘sounder’, which produces the familiar Morse code ‘dots’ and ‘dashes.’\u003c\/p\u003e\n\u003cp\u003eThe relay consist of vertically mounted electric coils, which are polarised by a magnet which fits around the coils. When the current passes through the relay, it can make two contacts (with either ‘S’ or ‘M’, depending on whether or not the polarity is reversed). Lifting the glass lid on the relay exposes the local contacts allowing adjustment to ‘S’ or ‘M’.\u003c\/p\u003e\n\u003cp\u003eThe letters on the wooden base:-\u003c\/p\u003e\n\u003cp\u003eS: Space\u003cbr\u003eM: Mark\u003cbr\u003eT Tongue\u003cbr\u003eD: Down\u003cbr\u003eU: Up\u003c\/p\u003e\n\u003cp\u003e\u003ca href=\"https:\/\/mullard-antiques-and-collectibles.myshopify.com\/collections\/morse-keys-telegraphy\" target=\"_blank\" rel=\"noopener noreferrer\"\u003eClick on this link for more vintage telegraphy and morse keys.\u003c\/a\u003e\u003c\/p\u003e\n\u003cstrong\u003e\u003c\/strong\u003e","brand":"General Post Office GPO","offers":[{"title":"Default Title","offer_id":31882338828332,"sku":"","price":0.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0303\/5122\/8972\/products\/DSC02205.jpg?v=1580120825","url":"https:\/\/mullardantiques.co.uk\/en-us\/products\/1920s-telegraph-gpo-standard-type-b-relay","provider":"Mullard Antiques and Collectibles","version":"1.0","type":"link"}