| WO1989006083A1
                (en) |  | Data transmission system | 
        
          | BE424095A
                (forum.php) |  |  | 
        
          | US2652446A
                (en) |  | Release signal for telegraph systems | 
        
          | US2599344A
                (en) |  | Telegraph exchange for lines with simplex or duplex characteristics | 
        
          | US2761896A
                (en) |  | Telegraph repeater system | 
        
          | US2337496A
                (en) |  | Multiway regenerative repeater | 
        
          | US717776A
                (en) |  | Quadruplex telegraph system. | 
        
          | US1891564A
                (en) |  | Circuit arrangement for telegraphic apparatus | 
        
          | US313787A
                (en) |  | Means for preventing | 
        
          | US707557A
                (en) |  | Telegraphic apparatus. | 
        
          | US2350589A
                (en) |  | Telephone or like system | 
        
          | US366695A
                (en) |  | Quadruplex telegraphy | 
        
          | BE528427A
                (forum.php) |  |  | 
        
          | US1242009A
                (en) |  | Impulse-control system. | 
        
          | BE486685A
                (forum.php) |  |  | 
        
          | US883530A
                (en) |  | Telegraph-repeater. | 
        
          | US1220756A
                (en) |  | Quadruplex telegraphy. | 
        
          | US2195973A
                (en) |  | Start-stop repeater system | 
        
          | BE353046A
                (forum.php) |  |  | 
        
          | US1470984A
                (en) |  | Signaling circuits | 
        
          | US2194063A
                (en) |  | Electrical signaling system | 
        
          | SU530659A3
                (ru) |  | Устройство дл дистанционного выключени телетайпной абонентской установки | 
        
          | GB373650A
                (forum.php) |  |  | 
        
          | US1205248A
                (en) |  | Printing-telegraph apparatus. | 
        
          | SU74607A1
                (ru) |  | Устройство обратного управлени в системе магистральной св зи совещаний |