Integrated circuit configurations and methods for providing functions for public telephones
Circuit configurations designed for use with public telephones to provide standard telephone functions with higher reliability, lower cost, and lower packaging densities, include first and second channel means for providing both transmit and receive multiplexing control, a one-wire compatible user interface, and embedded PIC microcontroller for both digital control and monitoring of analog measurement and multiplexing circuits, and bitstream format conversion techniques.
1. An integrated circuit for use in a public telephone to provide standard telephone functions, the integrated circuit comprising:
first channel means for providing a transmit multiplexing control;
second channel means for providing a receive multiplexing control; and
serial user interface means electronically coupled with the first and second channel means, the user interface means compatible with a single-wire timing protocol.
2. The integrated circuit recited in claim 1 , further comprising:
means for providing a digital/analog delta-sigma bitstream output from the integrated circuit; and wherein
the bitstream has an analog value written via the serial single-wire user interface means.
3. The integrated circuit recited in claim 1 , further comprising programmable interrupt controller means embedded in the integrated circuit.
4. The integrated circuit recited in claim 3 , wherein the programmable interrupt controller means comprises:
means for providing digital control; and
means for monitoring analog measurements and the first and second channel means.
5. The integrated circuit recited in claim 1 , further comprising digitally programmable gain control means.
6. The integrated circuit recited in claim 1 , further comprising multiple analog audio input means.
7. The integrated circuit recited in claim 6 , wherein said analog audio input means comprises at least four such inputs.
8. The integrated circuit recited in claim 1 , further comprising dual audio output means.
9. The integrated circuit recited in claim 1 , further comprising means for cancelling undesirable audio and frequency shift keying side band components.
10. The integrated circuit recited in claim 1 , further comprising means for providing signal selection and gain control for plural audio frequency, digital and analog inputs.
11. An integrated circuit for use in a public telephone to provide standard telephone functions, the integrated circuit comprising:
first channel means for providing a transmit multiplexing control;
second channel means for providing a receive multiplexing control;
means for providing analog inputs to the second channel means;
means for converting the analog inputs into a bitstream format; and
means for scaling the converted analog inputs.
12. The integrated circuit recited in claim 11 , wherein the means for scaling comprises an internal programmable gain switched capacitor amplifier.
13. The integrated circuit recited in claim 11 , wherein the means for converting the scaled audio inputs into a bitstream format comprises a delta sigma modulator circuit.
14. A method for controlling standard functions in a public telephone, comprising the steps of:
providing an integrated circuit;
configuring the integrated circuit with first channel means for providing a transmit multiplexing control and second channel means for providing a receive multiplexing control for audio inputs;
configuring the integrated circuit to include both audio and single bit bitstream inputs.
15. An integrated circuit for use in a public telephone to permit and control standard telephone functions, the integrated circuit comprising:
two channels of audio control, including a first channel functioning as a transmit multiplexing control and the second channel functioning as a receive multiplexing control;
means for converting the analog inputs into a single bit bitstream; and
means for scaling the converted analog inputs to the first and second channels.
16. The integrated circuit recited in claim 15 wherein the means for scaling the analog inputs to the first and second channels comprises an internal programmable gain switched capacitor amplifier.
17. The integrated circuit recited in claim 16 wherein the means for converting the analog inputs into a bitstream format comprises a delta-sigma modulator.
18. The integrated circuit recited in claim 17 further comprising single-wire interface means for providing control over the converted bitstream format.