Two-Wire Intercom Time Division Duplex Signal Transmission
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Solution Overview
Problem
Conventional intercom systems using two-wire cables for both analog and digital transmission face complexity and high costs due to the need for different frequency bands for uplink and downlink signals, making high-quality image display and low-cost telephone conversations difficult.
Innovation Solution
The intercom system employs time division duplex baseband transmission, where the front door slave unit and master unit packetize various data types and transmit them using the same frequency band, alternating between transmission and reception based on time division control, simplifying the circuit configuration and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different frequency bands are used for uplink and downlink signals in digital transmission, then full duplex communication is achieved, but device complexity and cost increase
Solution Approach 1:
The patent applies time division duplex (TDD) where uplink and downlink transmissions occur in alternating time slots on the same frequency band. The base station and terminal device synchronize their transmission and reception timing, with each side transmitting during its allocated time slot and listening during the other's slot, achieving full duplex communication without requiring separate frequency bands or complex frequency management circuits
Solution Approach 2:
The patent merges the uplink and downlink frequency bands into a single shared frequency band. By combining both communication directions into one frequency resource and separating them only in the time domain, the system reduces the number of required frequency bands and simplifies the circuit configuration while maintaining full duplex functionality
2Ease of manufacture
If analog transmission is used on two-wire cable, then existing cable infrastructure is utilized, but image signal transmission quality is insufficient
Solution Approach 1:
The patent replaces analog transmission with digital transmission on the two-wire cable. By converting image signals and other data into digital packets and transmitting them using digital modulation schemes, the system maintains compatibility with existing cable infrastructure while achieving high-quality image transmission comparable to coaxial cable or wireless connections
3Manufacturing precision
If digital transmission is implemented on two-wire cable, then image signal quality is improved, but the need for separate frequency bands increases cost and complexity
Solution Approach 1:
The patent uses time division duplex where digital transmission occurs in alternating time slots for uplink and downlink on the same frequency band. This periodic transmission pattern eliminates the need for separate frequency bands, reducing device complexity and cost while maintaining high-quality digital image transmission
Solution Approach 2:
The patent makes the single frequency band universal for both uplink and downlink communication. The same frequency resource serves dual purposes by being shared between transmission and reception through time division, eliminating the need for separate frequency bands and reducing overall system complexity
Data Source
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AI summary
There is provided an intercom system which realizes high-quality image display and communication with low cost. In the intercom system, front door slave unit 300 having an attached camera and master unit 400 are connected to each other through a two-wire cable, and communication between front door slave unit 300 and master unit 400 is performed with transmission and reception of an image signal. Front door slave unit 300 packetizes a control signal, an image signal, and a sound signal of front door slave unit 300, generates an uplink signal, and transmits the generated uplink signal to master unit 400. Master unit 400 packetizes a control signal and a sound signal of master unit 400, generates a downlink signal, and transmits the generated downlink signal to front door slave unit 300. Front door slave unit 300 and master unit 400 perform transmission of the uplink signal and transmission of the downlink signal in a manner of time division duplex using the two-wire cable.