Telephonic communications – Supervisory or control line signaling – Substation originated
Patent
1991-05-31
1993-08-31
Dwyer, James L.
Telephonic communications
Supervisory or control line signaling
Substation originated
379413, 379387, 379362, H04M 1900
Patent
active
052415910
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.
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Dwyer James L.
Rohm & Co., Ltd.
Shehata M.
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