Telephonic communications – Terminal – Switch or switch actuator structure
Reexamination Certificate
1999-03-09
2001-09-11
Chiang, Jack (Department: 2642)
Telephonic communications
Terminal
Switch or switch actuator structure
Reexamination Certificate
active
06289100
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a communications station having a Hall effect IC for placing the station on-hook or off-hook when the station handset is in the handset cradle or absent from the cradle. The invention also relates to a communications station for use in a distributed audio system having a Hall-effect integrated circuit (IC) mounted within a handset cradle of the communications station for placing the communications station on-hook or off-hook. The communications station can be used as a dedicated field party line telephone, page party or intercom system, and can employ carrier techniques for transmitting and receiving audio signals.
BACKGROUND OF THE INVENTION
A need exists for communication between personnel in large industrial and commercial facilities such as warehouses, power generating plants, refineries, manufacturing facilities, rail yards and sea ports, among other facilities. The use of radio communications is common; however, radio communications is not always effective in environments where the range of radio signals is limited by underground passageways, for example. Additionally, the ability to deliver emergency voice communications to a variety of personnel throughout a facility is difficult absent an accessible public address system.
One common system employs a page line and an audio line for station-to-station communications. In this manner, communications stations can be distributed throughout a facility and connected using page lines and audio party lines. Typically, only one conversation per party line can occur at a time, thereby limiting the number of simultaneous users to those who are parties to the conversation.
A user must first go off-hook to access the page line, page the desired party, tell the other party which alternate line to switch to, and release the page switch. Both parties must then switch to the same party line and go off-hook in order to converse. When the parties have completed their conversation, they must hang up the handset. Examples of known distributed audio systems are disclosed in U.S. Pat. No. 4,847,888 to Cox et al., U.S. Pat. No. 5,014,347 to Cox et al., U.S. Pat. No. 4,206,318 to Steely, U.S. Pat. No. 5,179,588 to Nowicki, U.S. Pat. No. 5,559,625 to Smith et al., and U.S. Pat. No. 5,033,080 to Deane.
For existing communications stations, on-hook/off-hook switching is accomplished using mechanical switches. For example, when the handset of a communications station is placed off-hook, a mechanical switch is activated to connect the telephone to the line. Such mechanical switches can be unreliable, large in size and expensive. Additionally, mechanical switches are generally exposed to environmental contaminants, for example, particulates or gases, which can corrode the mechanical switching mechanism and contacts. Other examples of harsh environmental conditions include exposure to moisture, corrosive vapors such as industrial chemicals or salt air, temperature extremes, particulates, radiation, electrical fields, stray magnetic fields, and the like. When exposed to these types of environments, the mechanical switches may corrode, become encrusted or otherwise become inoperable.
Alternatively, non-contact, magnetically-operated, reed switches have been used. The non-contact means are generally costly, more susceptible to stray electromagnetic fields, and less robust than mechanical switches. Reed switches, while generally sealed in an inert gas ampoule, may become inoperable when, for example, a fracture forms when exposed to temperature extremes, which may result in corrosion of the contacts. In another example, a stray magnetic field may cause the switch to become biased and therefore not respond properly.
Thus, there is a need for improved communications stations having reliable on-hook and off-hook switches that are small in size, low in cost and able to withstand harsh environmental conditions, and therefore are not susceptible to the corrosion of the contacts or weak stray magnetic fields.
SUMMARY OF THE INVENTION
Accordingly, an aspect of the present invention is a communications station having reliable on-hook and off-hook switches that can withstand harsh environments. A communications station such as a telephone has a handset support cradle which need not be physically a part of or connected to the body of the telephone. The handset support cradle can be disposed alongside the telephone body, or in the general proximity of the telephone body. This facilitates rapid replacement of components if necessary. A hook-switch board is preferably a part of the handset support cradle, and is electrically connected to the circuitry of the telephone.
In accordance with another aspect of the present invention, a communications station comprises a Hall-effect integrated circuit for on-hook and off-hook switching. A printed circuit board equipped with the Hall-effect device, HED, is mounted inside the communications station, or more specifically the handset cradle, in order to protect it from environmental effects. Additionally, the HED, and optionally the associated printed circuit board, can be coated or otherwise encapsulated in a protective material, for example, a solithane or a sealed plastic sheathing, for protection from harsh environmental conditions. Two HEDs are mounted on the printed circuit board for redundancy. Alternatively, two HEDs can be mounted on the printed circuit board so as to be inverted relative to each other. Each HED is directional. By utilizing inverted placement, a communications handset containing a magnet of unknown polarity can still reliably achieve on-hook/off-hook switching when placed near the HEDs.
In accordance with yet another aspect of the present invention, a field telephone is provided for use in a distributed audio system. The field telephone comprises a handset connected to a main telephone body. The handset generates a magnetic field caused by leakage flux from a magnet. A handset support cradle is attached to the telephone body and comprises a hook-switch board having a Hall-effect integrated circuit which reacts with the magnetic field when the handset is placed in the handset support cradle. The magnetic field affects the Hall-effect integrated circuit to place the field telephone in an on-hook state. Similarly, when the handset is removed from the handset support cradle, the magnetic field is removed from the Hall-effect integrated circuit, and the field telephone enters an off-hook state. The magnet can be a component of a receiver contained within the handset, or a separate component attached to the handset.
The distributed audio system includes a plurality of telephone lines, including a page line pair and a party line pair. Means are included in the telephone for selecting a telephone line pair and transmitting audio signals over the selected line pair to a receiving station. Each handset acts as a means for transmitting user audio signals to another connected telephone, and for receiving audio signals transmitted from another telephone. The Hall-effect integrated circuit performs the on-hook/off-hook switching of any selected and connected telephone line.
Other advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.
REFERENCES:
patent: 2322851 (1943-06-01), Kalb
patent: 3413423 (1968-11-01), Stevko
patent: 4022980 (1977-05-01), Kitajewski et al.
patent: 4103112 (1978-07-01), Korsky
patent: 4166928 (1979-09-01), Sabon
patent: 4206318 (1980-06-01), Steely
patent: 4300021 (1981-11-01), Van Husen
patent: 4355209 (1982-10-01), Sabon
patent: 4847888 (1989-07-01), Cox et al.
patent: 5014347 (1991-05-01), Cox et al.
patent: 5033080 (1991-07-01), Deane
patent: 5065088 (1991-11-01), Habiro et al.
patent: 5136630 (1992-08-01), Breneman et al.
patent: 5179588 (1993-01-01), Nowicki
patent: 5499292 (1996-03-01), Blonder et al.
patent: 5504813 (1996-04-01), Takasaki
patent: 5535272 (1996-07-01)
Farmer Charles M.
Ritter David T.
'Hubbell Incorporated
Bicks Mark S.
Chiang Jack
Goodman Alfred N.
Michel Christian C.
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