1
Brian H Breneman, Bruce Dale: Intrinsically safe telephone. Gai Tronics, Woodcock Washburn Kurtz Mackiewicz & Norris, August 4, 1992: US05136630 (43 worldwide citation)

An intrinsically safe telephone as provided for use in hazardous areas. The telephone includes a single line instrument located in the hazardous area which, in turn, is coupled by a two-wire transmission path to a shunt diode barrier and a telephone line interface located in a safe environment. The ...


2
Larry P Grandstaff: Intrinsically safe telephone. Gai Tronics, Woodcock Washburn Kurtz Mackiewicz & Norris, April 26, 1988: US04741031 (39 worldwide citation)

An intrinsically safe telephone as provided for use in hazardous areas. The telephone includes a single line instrument located in the hazardous area which, in turn, is coupled by a two-wire transmission path to a shunt diode barrier and a telephone line interface located in a safe environment. The ...


3
William Wheatley, Robert Roy Goff, William Charles Wheatley: Intrinsically safe telephone systems. Winster Engineering Group, Ostrolenk Faber Gerb & Soffen, December 20, 1977: US04064366 (8 worldwide citation)

An intrinsically safe telephone system for use in mines or similar hazardous areas including a battery charging circuit arranged to supply charging current of a predetermined low value to the battery of an operational unit located in the hazardous area during on-hook periods. A circuit is provided f ...


4
Michel L Oules: Intrinsically safe telephone network. S I L E C Division Signalisation Industrielle, Cushman Darby & Cushman, July 22, 1980: US04214127 (4 worldwide citation)

A telephone network which can be placed in a dangerous or explosive atmosphere is disclosed. The telephone network includes a manual exchange, one or more telephone sets and one or more limiter-repeater circuits connected with the telephone sets by telephone lines. The one or more telephone sets do ...


5
Improvements in circuit arrangements for connecting an intrinsically safe telephone station to an exchange which is not intrinsically safe. Siemens, September 19, 1962: GB906182-A

906,182. Automatic exchange systems. SIEMENS & HALSKE A.G. Dec. 7, 1960 [Dec. 8, 1959], No. 42113/60. Class 40 (4). A circuit arrangement for connecting a " safe " sub-station to an " unsafe " exchange includes a transformer LU, one winding of which is connected through a first circuit to the substa ...


6
Grandstaff Larry P: Telephone intrinsequement sur, Intrinsically safe telephone. Hubbell Incorporated, CASSAN MACLEAN, July 31, 1990: CA1272319

ABSTRACT An intrinsically safe telephone as provided for use in hazardous areas. The telephone includes a single line instrument located in the hazardous area which, in turn, is coupled by a two-wire transmission path to a shunt diode barrier and a tele-phone line interface located in a safe environ ...


7
Breneman Brian H, Dale Bruce: Telephone a securite intrinseque, Intrinsically safe telephone. Hubbell Incorporated, CASSAN MACLEAN, October 17, 2000: CA2036521

An intrinsically safe telephone as provided foruse in hazardous areas. The telephone includes a singleline instrument located in the hazardous area which, inturn, is coupled by a two-wire transmission path to a shuntdiode barrier and a telephone line interface located in asafe environment. The telep ...