Magneto Mining, Wall Switchboard
Designed to meet the case where a larger ultimate capacity than six lines is required.
Constructed on very similar lines to the N510 type overleaf but a micro-telephone with battery switching key, induction coil and generator are fitted so that a separate instrument is not required for operating purposes.
The indicators and keys are mounted on a hinged steel front plate which is locked by means of special triangle-headed screws. the keys are of exactly the same design as those used oil the "Pyramid" boards but are arranged to provide a limited number of connecting circuits as given below.
The generator is approved by the Mines Department as being electrically safe for use in fiery mines and provided that the other apparatus used in conjunction with the switchboards is of an approved type, the latter may be safely used in the mine.
Equipment's over 10 lines have the line indicators and connecting keys arranged horizontally and the clearing indicators vertically.
Switchboard No 552 on a stand is shown to the right.
|Code No.||Lines||Connecting Ccts||Dimensions inches|
|N550||10||3||20 x 15 x 9|
|N551||15||4||23.5 x 26.25 x 9|
|N552||20||4||19.75 x 32 x 7.75|
|N553||30||5||21 x 45 x 7.75|
|N554||30||5||23.5 x 36 x 9|
N554 was first shown in the Cat 26, Supplement 1932
N551 was introduced in the Cat 26, Supplement 1935
`A' variants are fitted with enclosed indicators, instead of drop indicators.
Taken from the Ericsson catalogue, edition 26
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