Two-Wire Video Door System Using BNFSK and PPM Modulation
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Solution Overview
Problem
Current video door systems using two-wire communications lines are limited to single simultaneous communication channels, require additional infrastructure, and are not adaptable to different cable types or topologies, making it difficult to transmit multiple audio and video conversations simultaneously while managing data and power supply.
Innovation Solution
A video door system employing digital BNFSK and PPM modulators and demodulators allows for simultaneous bidirectional audio and unidirectional video transmission over two-wire lines without additional infrastructure, using Time Division Multiplexing and adaptive modulation to support multiple conversations on conventional cabling, with power supply integrated into the communication line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If analog modulation (FM, AM, PM) is used to transmit audio and video channels simultaneously, then single conversation channel is achieved, but multiple simultaneous conversations cannot be established
Solution Approach 1:
The patent segments the communication channel into multiple time slots using Time Division Multiplexing (TDM). Each conversation channel is assigned a specific time slot, allowing multiple conversations to occur simultaneously on the same two-wire line. The multiplexer divides the composite signal into separate time-division multiplexed channels, enabling independent audio and video transmission for multiple conversations without interference.
Solution Approach 2:
The patent transitions from frequency-domain modulation (analog FM/PM) to time-domain multiplexing (digital TDM). By adding the time dimension to signal transmission, multiple conversations are multiplexed into separate time slots, allowing simultaneous communication channels without requiring additional frequency carriers or complex analog modulation schemes.
2Productivity
If more conductors are used to transmit multiple channels simultaneously, then multichannel communication is achieved, but infrastructure complexity and cost increase
Solution Approach 1:
The patent makes the two-wire communication line universal by enabling it to carry multiple conversation channels simultaneously through TDM. The same two wires that traditionally carried single-channel audio/video signals now support multiple concurrent conversations, eliminating the need for separate cabling for each channel and reducing infrastructure requirements.
Solution Approach 2:
The patent implements dynamic time-division multiplexing where the allocation of time slots can be flexibly adjusted. The system dynamically assigns time slots to different conversations based on operational requirements, allowing the infrastructure to adapt to varying communication needs without requiring physical reconfiguration of cabling or additional permanent infrastructure.
3Speed
If digital modulation (FSK, PSK, PPM) is used for data transmission, then transmission rate is improved, but uncharacterized two-wire line transmission becomes difficult
Solution Approach 1:
The patent changes the modulation parameters by using Frequency Shift Keying (FSK) with specific frequency pairs (e.g., 1200 Hz and 2400 Hz) that are well-suited for two-wire line transmission. These frequency parameters are selected to work effectively with the electrical characteristics of conventional two-wire cables, enabling digital data transmission without requiring specialized characterized transmission lines or complex equalization equipment.
4Ease of manufacture
If two-wire line is used without power supply infrastructure, then installation is simplified, but power consumption of devices cannot be supported
Solution Approach 1:
The patent merges the power supply function with the communication function by using the same two-wire line for both data transmission and power delivery. The system combines audio/video signal transmission, data communication, and electrical power supply into a single integrated two-wire infrastructure, eliminating the need for separate power wiring and simplifying installation while supporting device power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables simultaneous conversations between multiple devices with improved signal quality and reduced bandwidth requirements, allowing low-cost and high-feature devices to coexist without additional infrastructure, adaptable to various cable types and topologies, and efficient data transmission.
Implementation Method 1
a digital BNFSK (Binary Narrow Frequency Shift Keying) modulator and a digital BNFSK demodulator to transmit audio and data
Implementation Method 2
a digital PPM (Pulse Position Modulation) modulator and a digital PPM demodulator to transmit audio and video
Implementation Method 3
using Time Division Multiplexing and adaptive modulation to support multiple conversations on conventional cabling
Implementation Method 4
connectable, by means of a non-polarized two-wire communications line, to a plurality of home terminals, provided with an element selected between an intercom and a video intercom, to transmit audio, video, and data through the communications line
Data Source
AI summary
Two-wire multichannel video door system that comprises at least two street panels (20) with video camera (18) and home terminals, provided with an intercom, or with a monitor intercom. Characterized in that the street panels comprise the following: a digital BNFSK modulator and a digital BNFSK demodulator for transmitting audio and data to an intercom terminal, provided with a digital BNFSK modulator and a digital BNFSK demodulator; and a digital PPM modulator and a digital PPM demodulator for the transmission of audio and video to a monitor terminal, provided with a digital BNFSK modulator and a digital BNFSK demodulator and a digital PPM modulator and a digital PPM demodulator, to maintain at least two simultaneous bidirectional audio conversations between two terminals with two street panels, and to send video from the street panels to the terminals at the same time, using any type of conventional cabling.