Telephone keypads

A number of applications have been suggested in the literature in which an applied force has been used to generate an electrical signal. One application is in telephone keypads [53]. Other applications use the... 

Copolymers are best suited to applications that require low coefficient of ffiction such as electric kettles and water jugs, components with snap fits, chemical piunps, bathroom scales, telephone keypads and housing for domestic appliances. 

PBT is used in E E applications for its electrical insulation properties, good heat resistance and chemical resistance. The main applications or PBT in the electrical and electronics industry include specialist light bulbs and lamp holders, housings for sockets and switches, printed circuit board connectors and sockets, junction boxes, capacitor housings, electronic coimectors, fans and coil formers. Other applications include keytops for telephone keypads and LED displays. 

In the eleetric appliances industry POM is used to make casings, gearwheels, clutches, bearings, carriers and gears. In electronics, POM is used for telephone keypads, coil bobbins, switches, spring elements, armature supports, videocassettes, outsert boards for VCR, CD players and camcorders. 

The applications are automotive window seals and fiiel filler gaskets, industrial door and window seals and weatherstripping, wire/cable covering, and hand-held power tool housing/handles. Nonslip soft-touch hand-held tool handles provide weather and chemical resistance and vibration absorption.i Translucent grade is extruded into films for face masks and tube/hosing and injection-molded into flexible keypads for computers and telephones. Certain grades are paintable without a primer. Typical durometer hardnesses are Shore A 60, 76, and 80. 

A call is initiated by removing the handset from the cradle. This action removes the ringer from the circuit and connects the telephone s electronic apparatus. A circuit is established through this apparatus, which is detected by the central office. Equipment at the central office sends a dial tone to the subscriber. Hearing this dial tone, the subscriber dials a number—either with a true dial, which interrupts the two-wire circuit the indicated number of times, or a keypad, which transmits two tones to the central office. 

Commonly used transmission devices are telephones, which increasingly are cell phones, smartphones, or handheld computers. The dial is usually a set of pushbuttons (the keypad). The system converts the analogue signals of the unit to a digital signal (a series of ones and zeros). 

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