| GB421059A
                (en) |  | Improvements in devices for recording and reproducing telephonic messages | 
        
          | BE454021A
                (en0) |  |  | 
        
          | US1647796A
                (en) |  | Telephone system | 
        
          | US2295032A
                (en) |  | Communication exchange system | 
        
          | US1746327A
                (en) |  | Telephone system | 
        
          | US2025145A
                (en) |  | Transmission system | 
        
          | US2087398A
                (en) |  | Automatic switch for use in telephone or like systems | 
        
          | US1727137A
                (en) |  | Automatic telephone system | 
        
          | US2745903A
                (en) |  | Signaling system | 
        
          | US2036316A
                (en) |  | Telephone system | 
        
          | US2815404A
                (en) |  | Connection for automatic ring signal | 
        
          | US1557609A
                (en) |  | Printing-telegraph exchange system | 
        
          | US1107135A
                (en) |  | Telephone-exchange system and apparatus. | 
        
          | US1312688A
                (en) |  | Plancxtrai | 
        
          | US1521821A
                (en) |  | Repeater for automatic telephone systems | 
        
          | US2862058A
                (en) |  | Selector systems | 
        
          | US1963747A
                (en) |  | Telephone system | 
        
          | US1505715A
                (en) |  | Telephone system | 
        
          | US1857848A
                (en) |  | Communication system | 
        
          | US1132107A
                (en) |  | Automatic telephone system. | 
        
          | US1002878A
                (en) |  | Party-line telephone system. | 
        
          | US1722538A
                (en) |  | Automatic telephone system | 
        
          | US1339575A
                (en) |  | Machine-switching telephone-exchange system | 
        
          | US2996582A
                (en) |  | Discriminating trunk circuit | 
        
          | US1557991A
                (en) |  | Automatic telephone-exchange system |