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US 5,241,591 AGranted
Telephone system having a dial data changeover switch
AssigneeRohm Co., Ltd.
InventorMitsuro Saji
Life of this patent
Estimating the term…
Abstract
A telephone system having a dial data changeover switch transmits either a dial pulse signal or a dual-tone multifrequency signal along a telephone line. This telephone system includes a changeover switch for changing between a KEY signal from a key board and a control signal from a CPU. When a power interruption sensing device senses that the external power voltage is below a predetermined voltage, the changeover switch shunts from the control signal to the KEY signal and transmits either the DTMF signal or the DP signal along the telephone line.
Claims3
A telephone system comprising:
- (a) a key board;
- (b) a central processing unit for issuing a signal in response to a signal entered from the key board;
- (c) a power interruption sensing means for sensing when a voltage level of an external power supply drops below a predetermined level;
- (d) a selected signal transmitting means comprising a changeover switching means for outputting either the signal from the key board or the signal from the central processing unit in response to a signal from the power interruption sensing means, and an output means for outputting either a dual-tone-multi-frequency signal or a dial pulse signal in response to the output from the changeover switching means;
- and
- (e) a switching means for switching a drive current supply of the selected signal transmitting means from the external power supply to a telephone line current;
- wherein said changeover switching means applies the signal from the central processing unit to the output means when the voltage level of the external power supply is above the predetermined level and applies the signal from the key board to the output means when the voltage level of the external power supply is below the predetermined level.
4 more elements
Dependencies are inferred from the claim text.