Phone busy circuit
First Claim
Patent Images
1. A circuit for placing a busy signal on a telephone line while a computer is resetting, said telephone line having a TIP signal and a RING signal, said circuit comprising:
- decoder means for receiving a system address from said computer and for providing a decoder output signal in response to access of a predetermined system address by said computer;
memory means for entering a first state in response to a system reset signal received from said computer and for entering a second state in response to said decoder output signal;
a resistor; and
switching means for connecting said resistor between said TIP signal and said RING signal only when said memory means is in said first state.
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Accused Products
Abstract
A switching circuit places a load across the TIP and RING signals of a telephone line when the computer is reset and removes the load when the computer accesses a selected memory location. Thus, the telephone line remains in an off-hook state after the computer is reset and remains in that state until the computer executes software that causes the telephone line to return to the on-hook state. The computer may also execute software that causes the telephone line to enter the off-hook state.
55 Citations
14 Claims
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1. A circuit for placing a busy signal on a telephone line while a computer is resetting, said telephone line having a TIP signal and a RING signal, said circuit comprising:
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decoder means for receiving a system address from said computer and for providing a decoder output signal in response to access of a predetermined system address by said computer; memory means for entering a first state in response to a system reset signal received from said computer and for entering a second state in response to said decoder output signal; a resistor; and switching means for connecting said resistor between said TIP signal and said RING signal only when said memory means is in said first state. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A circuit for placing a busy signal on a telephone line while a computer is resetting, said telephone line having a TIP signal and a RING signal, said circuit comprising:
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a PAL for receiving a system address from said computer and for providing a decoder output signal in response to access of a predetermined system address by said computer; a flip-flop for entering a first state in response to a system reset signal received from said computer and for entering a second state in response to said decoder output signal; a resistor; and an opto-isolator for connecting said resistor between said TIP signal and said RING signal only when said flip-flop is in said first state. - View Dependent Claims (9, 10)
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11. A method for placing a busy signal on a telephone line having a TIP signal and a RING signal while a computer is resetting, comprising the steps of:
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placing a resistor across said TIP signal and said RING signal in response to a RESET signal from a computer; and removing said resistor from across said TIP signal and said RING signal in response to access of a predetermined system address by said computer. - View Dependent Claims (12, 13, 14)
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Specification