| Abbreviations
         A.T. - Automatic 
        B.E. - Branch Exchange 
        C.B. - Common Battery 
        C.B.S. - Common Battery Signalling 
        D.C. - Double Cord 
        F.P. - Floor Pattern 
        L.B. - Local Battery 
        N.T. - National Telephone Co. 
        S.C. - Single Cord 
        T.E. - Telephone Exchange 
        W.P. - Wall Pattern How P.M.B.X.s are described:- 
		They are generally described by the main circuit diagram followed by a fractional 
		suffix representing Equipment/Capacity. E.G. Switchboard CB 873 
		3+10 
                                           
		25 
		CB 873 is the main circuit diagram. 
		3+10 is the equipment/capacity of 3 exchange lines and 10 extension 
		lines as supplied. 
		25 is the ultimate total capacity of 5 exchange lines and 20 extensions 
		lines. 
		 
		 
		 
		 
		 
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