How Self-Healing Data Loops Automatically Elect a New Master Controller
A communication system where multiple nodes in a loop can automatically take over as the master controller if the current one fails, ensuring the network stays synchronized.
Original patent title: “Data communication system and method and communication controller and method therefor, having a data/clock synchronizer and method”
A communication system where multiple nodes in a loop can automatically take over as the master controller if the current one fails, ensuring the network stays synchronized. Granted to Process Systems Inc in 1987 with 58 claims and 83 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
This patent describes a network of devices connected in a loop where every device is capable of acting as either a 'master' or a 'slave'. The master node provides the master clock, which keeps all other nodes (slaves) synchronized so they can pass data reliably. If the master node fails or is removed, the other nodes detect the silence and use a timing mechanism to decide which one will become the new master. This allows the network to stay operational without manual intervention, effectively creating a self-healing communication loop.
The gap
What does this patent NOT cover?
- Does not cover networks that rely on a central server that cannot be replaced by a node.
- Does not cover non-synchronous communication systems that do not use a master clock.
- Does not cover systems where the master node is fixed and cannot be reassigned to another node.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The system assigns each node a different 'waiting time' after a failure is detected before it attempts to become the master, preventing multiple nodes from trying to take control at the exact same time.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Token ring network architectures
Industrial fieldbus communication systems
Redundant serial data loops in factory automation
Why it matters
The bigger picture
This technology was a foundational step in building resilient industrial control systems and local area networks. By allowing nodes to self-elect a master, it eliminated the single point of failure that plagued early serial communication loops, making systems more reliable for factory automation and data transmission.
Filed
February 15, 1983
Granted
June 30, 1987
Market context
Who's building on this
Companies in this space
The principles of master-slave election and fault-tolerant loops are now standard in industrial automation protocols like EtherCAT and various fieldbus technologies. Companies like Siemens, Rockwell Automation, and Beckhoff utilize similar logic to ensure high availability in their control networks.
Market impact
This patent helped shift the industry toward decentralized, self-healing network architectures. It provided a blueprint for engineers to design serial loops that could survive the loss of a primary controller, which became a critical requirement for safety-sensitive industrial and telecommunications environments.
Claim 1 — Plain English
What this patent covers
This patent describes a network of devices connected in a loop where every device is capable of acting as either a 'master' or a 'slave'. The master node provides the master clock, which keeps all other nodes (slaves) synchronized so they can pass data reliably. If the master node fails or is removed, the other nodes detect the silence and use a timing mechanism to decide which one will become the new master. This allows the network to stay operational without manual intervention, effectively creating a self-healing communication loop.
The clever bit
The system assigns each node a different 'waiting time' after a failure is detected before it attempts to become the master, preventing multiple nodes from trying to take control at the exact same time.
What it does not cover
- Does not cover networks that rely on a central server that cannot be replaced by a node.
- Does not cover non-synchronous communication systems that do not use a master clock.
- Does not cover systems where the master node is fixed and cannot be reassigned to another node.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Moderate
Citation count
38/40
Highly cited
Claim breadth
20/20
Very broad protection
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$60K – $194K
Midpoint $121K · expired or expiring · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Patent Claims
0 independent claims · 1 dependent
Claims are the legal boundaries of the patent. An independent claim stands alone. A dependent claim adds limitations to its parent, narrowing — but not broadening — the scope.
The original legal language
Original claims
58 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Circo, M. M. (1987). How Self-Healing Data Loops Automatically Elect a New Master Controller (U.S. Patent No. 4,677,614). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/4677614/data-communication-system-and-method-and-communication-controller-and-method-therefor-having-a-dataclock-synchronizer-and-method
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Self-Healing Data Loops Automatically Elect a New Master Controller cover?
A communication system where multiple nodes in a loop can automatically take over as the master controller if the current one fails, ensuring the network stays synchronized.
Who owns patent US 4677614?
Process Systems Inc owns this patent, granted in 1987.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 4677614 cited by?
This patent has been cited by 83 later patents that build on its ideas.
What problem does this patent solve?
This technology was a foundational step in building resilient industrial control systems and local area networks. By allowing nodes to self-elect a master, it eliminated the single point of failure that plagued early serial communication loops, making systems more reliable for factory automation and data transmission.
What does this patent NOT cover?
Does not cover networks that rely on a central server that cannot be replaced by a node.
Patent monitoring