DAA hook switch
AssigneeIntegration Associates Inc.
InventorsWayne T. Holcombe, Matthijs D. Pardoen
Life of this patent
Estimating the term…
Abstract
A hook switch circuit is shown wherein two high-voltage bipolar transistors, a PNP transistor Q1 and a NPN transistor Q2. that are connected in a regenerative feedback manner to form a bi-stable latch. The regenerative structure permits the use of low beta transistors that may be turned on with a low control current, but still conduct a sufficient off-hook current. Also shown is a polarity steering regenerative switch (MP1, MP2) that provides a power supply voltage from a telephone line pair and may be adapted for a polarity signal and can be combined with a current mirror (MP7) to produce a current signal proportional to the line voltage (LV1).
Claims18
A hook switch circuit for use in a telephone line interface circuit, the circuit comprising:
- a PNP transistor having a base, an emitter and a collector;
- an NPN transistor having a base, an emitter and a collector, where the emitter of the NPN transistor is coupled to the base of the PNP transistor;
- a first resistor coupled between the base of the NPN transistor and the emitter of the PNP transistor;
- and
- a second resistor coupled between the base of the PNP transistor and the source of the PNP transistor.
A telephone line interface circuit, the circuit comprising:
- a first bipolar transistor having a base, emitter and collector, the emitter being electrically coupled to the telephone line;
- a first resistor coupled between the base and the emitter of the first transistor;
- a second bipolar transistor having a base, emitter and collector, the emitter of the second transistor being coupled to the base of the first transistor;
- a second resistor coupled between the collector of the first transistor and the base of the second transistor;
- a line side circuit including a hook switch control, the line side circuit having an off-hook power supply terminal coupled to the emitter of the second transistor, a hook switch control terminal coupled to the base of the second transistor, and first and second on-hook supply terminals for coupling to a TIP and RING of the telephone line, where the hook switch control is configured to operate in an on-hook state from power supplied from the TIP and RING through the first and second on-hook supply terminals, and where the hook switch control is configured to receive a hook signal having first and second states, where the hook switch control outputs current at the hook signal terminal responding to the off-hook state of the hook signal and outputs no current at the hook signal terminal responding to the on-hook state of the hook signal;
- a third resistor having high impedance and coupled between the TIP of the telephone line and the first on-hook supply terminal;
- and
- a fourth resistor having high impedance and coupled between the RING of the telephone line and the second on-hook supply terminal
The telephone line interface circuit of clam 14, where the polarity steering regenerative switch circuit includes a buffer for generating, a logic level line polarity signal.
A power circuit for a line powered telephone interface circuit, the power circuit comprising:
- a first input/output pin configured to be coupled to a first terminal of a telephone line pair through a first high impedance resistor;
- a second input/output pin configured to be coupled to a second terminal of a telephone line pair through a second high impedance resistor;
- and
- a polarity steering regenerative switch electrically coupled to the first and second input/output pins such that the switch receives power from the first and second terminals of the telephone line pair through the first and second high impedance resistors.
Dependencies are inferred from the claim text.