Exploring Reverse Vending Machine For Mobile Phone: Technical Specifications, Structure, and Performance Insights

Types of Reverse Vending Machines for Mobile Phones

A reverse vending machine (RVM) for mobile phones is an innovative solution designed to promote electronics recycling by accepting used or outdated smartphones, tablets, and related components. These machines play a crucial role in reducing e-waste, recovering valuable materials like gold, silver, and rare earth elements, and encouraging sustainable consumer behavior. Depending on their design, capacity, and technological features, RVMs vary significantly to meet different operational needs—from small retail setups to large-scale recycling centers.

Single-Feed Machines

Designed for simplicity and ease of use, single-feed reverse vending machines accept one mobile device at a time per transaction. These compact units are ideal for locations with limited space and lower recycling volume.

Advantages

• Compact and easy to install
• Low maintenance requirements
• User-friendly interface
• Ideal for public spaces like malls and retail stores

Limitations

• Limited throughput capacity
• Not suitable for high-volume collection
• Slower processing during peak times

Best for: Small businesses, educational institutions, low-traffic urban areas

Multi-Feed Machines

These advanced RVMs allow users to deposit multiple mobile devices in a single session, increasing efficiency and convenience. Equipped with internal sorting mechanisms, they can process several phones sequentially without manual intervention.

Advantages

• Higher processing speed
• Improved user throughput
• Supports bulk drop-offs by individuals or families
• Reduces queue times in busy environments

Limitations

• Larger footprint than single-feed models
• Higher initial investment
• More complex internal mechanisms may require skilled servicing

Best for: Shopping centers, corporate campuses, community recycling events

Bulk-Deposit Machines

Built for industrial-scale operations, bulk-deposit reverse vending machines are engineered to handle large volumes of returned mobile phones. Often featuring conveyor belts, automated hoppers, or palletized storage, these systems streamline the intake process for recycling facilities and logistics hubs.

Advantages

• Extremely high capacity and throughput
• Automated handling reduces labor costs
• Seamless integration with warehouse management systems
• Supports large-scale e-waste collection programs

Limitations

• Requires significant space and infrastructure
• High purchase and installation cost
• Typically not accessible to individual consumers

Best for: Recycling centers, logistics depots, government e-waste initiatives

Smart Machines with IoT Integration

These next-generation RVMs leverage Internet of Things (IoT) technology to provide real-time data connectivity. They monitor device intake, user interactions, machine performance, and even environmental impact metrics such as CO₂ savings from recycled electronics.

Advantages

• Remote monitoring and diagnostics
• Real-time analytics and reporting
• Predictive maintenance alerts
• Integration with digital platforms and apps

Limitations

• Dependent on stable internet connection
• Higher cybersecurity considerations
• Increased complexity in setup and management

Best for: Smart cities, corporate sustainability programs, research and policy evaluation

Incentive-Based Machines

Incentive-based reverse vending machines reward users for recycling their old mobile phones through vouchers, discounts, charitable donations, or digital credits. These machines are powerful tools for driving public participation in e-waste reduction campaigns.

Advantages

• Boosts user engagement and recycling rates
• Promotes environmental awareness
• Flexible reward options (cashback, gift cards, donations)
• Supports marketing and brand loyalty initiatives

Limitations

• Ongoing cost of incentives
• Potential for misuse or fraudulent deposits
• Requires partnership with retailers or charities

Best for: Retail partnerships, environmental campaigns, urban sustainability drives

Type	Capacity	Technology Level	User Engagement	Ideal Setting
Single-Feed	Low (1 device/transaction)	Basic	Moderate	Retail stores, schools, offices
Multi-Feed	Medium (Multiple devices/session)	Intermediate	High	Shopping malls, community centers
Bulk-Deposit	Very High (Industrial volume)	Advanced	Low (Operator-focused)	Recycling plants, warehouses
Smart IoT Machines	Variable	High-Tech	Very High (Data-driven)	Smart cities, research programs
Incentive-Based	Low to Medium	Intermediate to High	Extremely High	Public campaigns, retail zones

Expert Tip: For maximum impact, combine incentive-based RVMs with smart IoT capabilities—this allows organizations to not only boost participation but also gather valuable data on recycling trends and user behavior for long-term sustainability planning.

Material & Durability of Reverse Vending Machines for Mobile Phones

Reverse vending machines (RVMs) designed for mobile phone recycling are engineered to withstand continuous public use, environmental exposure, and mechanical stress. The selection of high-performance materials for each component ensures long-term reliability, operational efficiency, and protection of valuable recycled devices. From rugged exteriors to precision internal systems, every part is carefully constructed to meet the demands of urban, outdoor, and high-traffic environments.

Outer Casing: Built to Withstand Abuse and Weather

Stainless Steel Enclosures

The outer casing of most commercial-grade reverse vending machines is constructed from stainless steel or powder-coated carbon steel. Stainless steel is highly favored for outdoor installations due to its exceptional resistance to corrosion, impact, and vandalism. Its non-porous surface resists graffiti, dents, and rust—even in coastal or high-humidity environments.

Additionally, stainless steel provides structural rigidity, protecting sensitive electronics from tampering or accidental damage. Many models feature reinforced corners and anti-pry edges to deter theft and forced entry.

Heavy-Duty Plastics & Composites

In indoor or semi-protected settings, manufacturers may use high-impact polymers such as polycarbonate or ABS (acrylonitrile butadiene styrene). These materials are lightweight, cost-effective, and resistant to cracking under temperature fluctuations.

Modern composite blends often include UV stabilizers and flame-retardant additives, making them suitable for shopping malls, airports, and retail spaces. While not as robust as metal, these plastics offer design flexibility and can be molded into sleek, user-friendly shapes that enhance aesthetics and ergonomics.

Interior Compartment: Resisting Wear and Chemical Exposure

The interior components that handle deposited mobile phones—such as chutes, guides, and inspection zones—are typically fabricated from polymer composites or galvanized steel. These materials are chosen for their ability to endure constant mechanical interaction with phones of varying sizes, weights, and conditions.

Polymer composites like reinforced nylon or fiberglass offer excellent abrasion resistance and low friction, allowing smooth phone transport without scratching or jamming. Galvanized steel, with its zinc coating, prevents rust caused by moisture or battery leakage from decommissioned devices—critical since damaged lithium-ion batteries can emit corrosive residues.

Interior surfaces are often treated with antimicrobial coatings, especially in high-touch urban environments, to maintain hygiene and reduce maintenance frequency.

Sensors and Mechanical Systems: Precision and Longevity

The functionality of a reverse vending machine relies heavily on advanced sensor technology. These sensors—used for scanning barcodes, identifying phone models via optical recognition, assessing condition, and sorting by material composition—are typically housed in ceramic or electronic-grade thermoplastics.

Ceramic Sensors

Ceramic-based sensors offer superior thermal stability and electrical insulation, making them ideal for environments with fluctuating temperatures. They are highly resistant to wear and electromagnetic interference, ensuring consistent performance over thousands of cycles.

Engineered Plastics

Electronic-grade plastics such as PEEK (polyether ether ketone) or PTFE (Teflon) are used in moving parts and sensor housings due to their low coefficient of friction, chemical resistance, and dimensional stability. These materials prevent static buildup and protect delicate circuitry from moisture and dust ingress.

Together, these materials enable accurate, fast processing while minimizing downtime due to sensor failure or calibration drift.

Collection Bins: Security and Device Protection

Once processed, phones are stored in secure collection bins before retrieval by service personnel. These bins are constructed from either high-density polyethylene (HDPE) or welded steel, each offering distinct advantages:

Bin Material	Security Level	Durability	Best Use Case
High-Density Polyethylene (HDPE)	Moderate	High impact resistance, lightweight	Indoor locations, low-theft risk areas
Welded Steel with Locking Mechanism	Very High	Extreme durability, tamper-proof	Outdoor deployments, high-traffic zones

Steel bins are often equipped with locking mechanisms, alarm triggers, and remote monitoring integration to prevent unauthorized access. HDPE bins, while less secure, are easier to transport and replace, and their non-conductive nature reduces the risk of short circuits from leaking batteries.

Water and Dust Resistance: IP-Rated Protection

To ensure reliable operation in diverse environments, most modern reverse vending machines feature IP (Ingress Protection)-rated enclosures. The IP rating is an international standard (IEC 60529) that defines the level of protection against solid particles and liquids.

IP54: Dust-protected and resistant to water splashes from any direction—suitable for covered outdoor areas or indoor public spaces.

IP65: Fully dust-tight with protection against low-pressure water jets—ideal for exposed outdoor installations like sidewalks or transit hubs.

IP66/IP67: High-level protection against heavy water jets or temporary immersion—used in extreme climates or coastal regions.

Higher IP ratings not only protect internal electronics but also help preserve the condition of collected phones by preventing moisture exposure. Sealed gaskets, drainage channels, and ventilation filters are integrated into the design to maintain airflow without compromising protection.

Important: Regular inspection and maintenance of seals, sensors, and bin integrity are essential to preserve the machine’s durability and performance. Even the most robust materials can degrade over time if exposed to extreme conditions without proper care. Always follow manufacturer guidelines for cleaning, part replacement, and software updates to maximize lifespan and recycling efficiency.

Commercial Use Cases of Reverse Vending Machines for Mobile Phones

Reverse vending machines (RVMs) are transforming the way organizations manage electronic waste by offering a smart, automated solution for mobile phone recycling. These innovative systems not only streamline the collection of used devices but also promote environmental responsibility, enhance customer engagement, and support corporate sustainability goals. By integrating incentives such as discounts, loyalty points, or charitable contributions, RVMs turn e-waste into a valuable resource while fostering a circular economy.

Retail Stores

Electronics retailers and mobile service providers can integrate reverse vending machines into their storefronts to create a seamless recycling experience for customers. By placing RVMs near checkout counters or product displays, stores encourage trade-ins during new device purchases.

• Offer instant rewards like store credit, discounts on new phones, or loyalty program points to incentivize participation
• Strengthen brand image by demonstrating environmental leadership and customer care
• Generate additional foot traffic and increase average transaction value through trade-in promotions
• Collect data on device models and conditions to inform inventory and refurbishment strategies

Business benefit: Enhances customer retention and drives repeat visits through reward-based recycling programs

Educational Institutions

Schools, colleges, and universities can deploy reverse vending machines across campuses to promote digital responsibility and environmental education. Strategically located in student centers, libraries, or dormitories, these machines serve both practical and pedagogical purposes.

• Provide students with campus credits, meal plan additions, or textbook vouchers for recycling old phones
• Partner with environmental clubs to run awareness campaigns and track collective impact
• Donate proceeds or recycled materials to sustainability projects or community initiatives
• Integrate with STEM curricula to teach about e-waste, resource recovery, and circular economy principles

Educational impact: Cultivates eco-conscious behavior in future generations while reducing campus e-waste

Events and Festivals

Event organizers can leverage reverse vending machines at concerts, tech expos, conferences, and music festivals to engage attendees in sustainable practices. Temporary installations offer high visibility and immediate rewards.

• Distribute event-specific incentives such as VIP access, merchandise, or raffle entries for phone drop-offs
• Create interactive displays showing real-time recycling metrics and environmental impact
• Partner with sponsors to brand machines and amplify messaging around corporate sustainability
• Reduce post-event waste management costs by diverting e-waste from landfills

Engagement strategy: Turns recycling into an experiential activity that boosts attendee satisfaction and social sharing

Corporate Offices

Forward-thinking companies are installing reverse vending machines in office lobbies, break rooms, or IT departments to support internal sustainability programs and corporate social responsibility (CSR) goals.

• Enable employees to easily recycle personal and company-issued devices at end-of-life
• Extend functionality to accept tablets, smartwatches, and other small electronics
• Track recycling metrics for ESG (Environmental, Social, and Governance) reporting and compliance
• Boost employee morale by aligning with shared values of environmental stewardship

CSR advantage: Demonstrates tangible commitment to sustainability, enhancing employer branding and stakeholder trust

Government Initiatives

Municipalities and national governments are deploying reverse vending machines in public spaces—such as transit stations, community centers, and municipal buildings—to improve e-waste collection rates and public engagement.

• Offer citizens digital coupons, transportation credits, or tax incentives for recycling mobile devices
• Implement gamified experiences with leaderboards and achievement badges to increase participation
• Ensure secure data destruction and chain-of-custody compliance for all collected devices
• Use aggregated data to monitor e-waste trends and inform policy decisions

Public benefit: Increases accessibility to recycling services while promoting civic responsibility and environmental protection

Additional Applications

Beyond the primary use cases, reverse vending machines can be adapted for various specialized environments:

• Shopping Malls: Centralized drop-off points with rewards redeemable across multiple stores
• Public Transit Hubs: High-traffic locations ideal for maximizing visibility and usage
• Hospitals & Healthcare Facilities: Secure disposal of outdated communication devices with HIPAA-compliant data wiping
• Refurbishment Centers: Integrated sorting and grading systems to streamline device reuse pipelines

Innovation opportunity: AI-powered diagnostics can assess device condition and value in real time

Strategic Recommendation: Organizations should consider partnering with certified e-waste recyclers and data security providers when implementing reverse vending solutions. This ensures compliance with environmental regulations (such as WEEE and GDPR) and builds consumer trust. Additionally, integrating RVMs with digital platforms allows for personalized user experiences, targeted marketing, and valuable insights into consumer behavior and device lifecycle patterns.

Sector	Primary Incentive	Key Benefit	Expected Impact
Retail Stores	Discounts / Loyalty Points	Increased Customer Retention	20-35% higher trade-in participation
Educational Institutions	Campus Credits / Charity Donations	Sustainability Education	15-25% reduction in student e-waste
Events & Festivals	Tickets / Merchandise	Brand Engagement	500+ devices collected per major event
Corporate Offices	Recognition / CSR Metrics	Employee Satisfaction	30-50% of staff participate annually
Government Programs	Vouchers / Tax Incentives	Public Accessibility	10-20% increase in e-waste diversion

Best Practices for Implementation

• User Experience: Ensure machines are intuitive, ADA-compliant, and available in multiple languages
• Data Security: Partner with certified providers for guaranteed data erasure and audit trails
• Maintenance: Schedule regular servicing to prevent downtime and ensure hygiene
• Visibility: Use clear signage and digital displays to communicate benefits and instructions
• Analytics: Leverage built-in reporting tools to measure performance and optimize placement
• Partnerships: Collaborate with environmental NGOs, recyclers, and technology brands for expanded reach

How To Choose the Right Reverse Vending Machine for Mobile Phones

Selecting the ideal reverse vending machine (RVM) for mobile phone recycling is a strategic decision that can significantly impact sustainability goals, customer engagement, and operational efficiency. Whether you're a retailer, municipality, educational institution, or environmental organization, choosing the right RVM involves evaluating several key factors. This comprehensive guide outlines the essential considerations to help you make an informed decision tailored to your specific needs.

Important Note: Mobile phone RVMs differ significantly from beverage can or bottle recyclers due to the complexity of electronics identification, data security, and value assessment. Always ensure the machine is specifically designed for e-waste and mobile devices, not general-purpose recycling.

Assess Your Recycling Needs and Volume

Understanding your recycling objectives and expected throughput is the foundation of selecting the right RVM. Begin by analyzing the scale and scope of your recycling program:

• Single vs. Multi-Feed Systems: Single-feed machines accept one device at a time and are ideal for low-traffic areas like small retail stores or offices. Multi-feed systems allow simultaneous deposits and are better suited for high-traffic zones such as shopping malls, transit hubs, or university campuses.
• Capacity Requirements: Estimate the average number of phones collected daily or weekly. Small units may hold 20–50 devices, while industrial-grade models can store over 200 phones. Consider models with remote monitoring to alert staff when nearing capacity.
• Device Compatibility: Ensure the RVM can identify a wide range of smartphones, tablets, and accessories. Look for machines that support global models across brands like Apple, Samsung, Google, and others.

Choose the Optimal Location and Build Quality

The installation environment plays a crucial role in determining the appropriate RVM design and durability:

• Indoor vs. Outdoor Placement: Indoor units can feature sleek, modern designs that complement retail or office aesthetics. Outdoor installations require rugged, weather-resistant enclosures made from powder-coated steel or aluminum to withstand rain, dust, UV exposure, and potential vandalism.
• Security Features: Machines in public or unattended areas should include anti-tamper alarms, reinforced locking mechanisms, GPS tracking, and surveillance camera integration to protect collected devices and deter theft.
• Ergonomic Design: The unit should be accessible to all users, including those with disabilities. Consider height, screen readability, and ease of use for seniors or first-time recyclers.

Design Effective Incentive Programs

User engagement is directly influenced by the rewards offered. A well-designed incentive system encourages repeat participation and builds brand loyalty:

• Reward Options: Choose machines that support flexible redemption methods such as instant gift cards (e.g., Amazon, Starbucks), store discounts, loyalty points, or donations to environmental charities.
• Target Audience Alignment: For younger demographics, digital rewards and social sharing options (e.g., "I recycled my phone!") can boost participation. Corporate programs may prefer points redeemable for company perks.
• Real-Time Payouts: Ensure the RVM provides immediate feedback and rewards upon deposit to reinforce positive behavior and reduce user frustration.

Leverage Sorting, Data Collection, and IoT Integration

Modern RVMs go beyond collection—they serve as data hubs for sustainability reporting and operational insights:

• Advanced Identification Technology: Look for machines equipped with AI-powered imaging, barcode scanning, and model detection to accurately assess device condition and value.
• IoT and Cloud Connectivity: Connected RVMs provide real-time analytics on collection rates, user demographics, peak usage times, and device types. This data is invaluable for campaign optimization and ESG (Environmental, Social, and Governance) reporting.
• Compliance Tracking: For businesses or municipalities subject to e-waste regulations, select machines that generate audit trails and certification of responsible recycling, ensuring compliance with WEEE, R2, or local standards.

Plan for Budget and Total Cost of Ownership

While upfront cost is important, a thorough financial evaluation should include long-term expenses and return on investment:

• Initial Investment: Prices vary widely—from $3,000 for basic models to $15,000+ for advanced, connected units. Determine which features are essential versus optional.
• Ongoing Costs: Factor in maintenance contracts, software updates, cleaning, transportation of collected devices, and potential staffing needs for restocking rewards or emptying bins.
• Revenue Opportunities: Some providers offer revenue-sharing models where you earn a percentage of the resale value of collected phones, helping offset operational costs.
• Leasing vs. Buying: Consider leasing options for short-term campaigns or pilot programs to reduce capital expenditure.

Selection Factor	Key Questions to Ask	Recommended Features	Best For
Recycling Volume	How many phones do you expect to collect monthly?	Capacity alerts, multi-feed capability	High-traffic public spaces
Location	Will the machine be indoors, outdoors, or in a semi-secure area?	Weatherproof casing, anti-vandal design	Malls, transit stations, campuses
Incentives	What motivates your target users to recycle?	Multiple reward options, instant payout	Retailers, loyalty programs
Data & Analytics	Do you need usage reports or compliance documentation?	IoT connectivity, cloud dashboard	Corporations, municipalities
Budget	Is this a short-term campaign or long-term investment?	Leasing options, low maintenance	Nonprofits, pilot programs

Pro Tip: Before making a purchase, request a demo unit for a trial period. This allows you to evaluate user interaction, reliability, and integration with your existing systems in real-world conditions—helping avoid costly mistakes.

Additional Recommendations

• Partner with certified e-waste recyclers to ensure collected phones are responsibly processed and data securely erased.
• Train staff or volunteers to assist users during initial deployment to increase adoption rates.
• Integrate the RVM into broader sustainability campaigns with signage, social media promotion, and educational materials.
• Regularly update software to maintain security, improve recognition accuracy, and add new device models.
• Monitor performance metrics monthly to assess ROI and user engagement trends.

Choosing the right reverse vending machine for mobile phones is more than a technical decision—it's a commitment to environmental responsibility and user convenience. By carefully evaluating your recycling needs, location, incentive strategy, data requirements, and budget, you can select a solution that delivers lasting value. Whether your goal is reducing e-waste, enhancing customer experience, or meeting regulatory standards, the right RVM can become a powerful tool in your sustainability toolkit.

Frequently Asked Questions About Reverse Vending Machines for Mobile Phones

Q1: What is the purpose of a reverse vending machine for mobile phones?

Reverse vending machines (RVMs) for mobile phones are designed to promote responsible e-waste recycling by offering a convenient and rewarding way for users to return their old or unused devices. These automated systems accept discarded phones and provide instant incentives—such as gift cards, discounts, or charitable donations—in exchange. This not only encourages consumers to recycle but also helps prevent hazardous materials from ending up in landfills.

By streamlining the collection process, RVMs play a vital role in recovering valuable materials like gold, silver, copper, and rare earth elements, which can be reused in new electronics. This supports a circular economy and reduces the environmental impact of mining and manufacturing.

Q2: Which materials are commonly used to construct recycling machines?

Recycling machines, especially those designed for outdoor or high-traffic environments, are built using robust and long-lasting materials to ensure durability and reliability. The primary construction materials include:

• Steel: Used for the machine’s frame and exterior casing due to its strength, resistance to impact, and ability to deter vandalism.
• Heavy-Duty Plastics: Employed in non-structural components and internal mechanisms where flexibility and corrosion resistance are important.
• Polyethylene: Often used for collection bins and internal storage compartments because it is lightweight, resistant to moisture, and easy to clean.

These materials are selected not only for their resilience but also for their sustainability—many are recyclable themselves, aligning with the machine’s environmental mission.

Q3: How durable are these machines when it comes to outdoor use?

Yes, most reverse vending machines designed for outdoor deployment are highly durable and built to withstand a variety of environmental conditions. They typically feature an IP (Ingress Protection) rating, such as IP54 or higher, which means they are protected against dust ingress and water splashes from any direction.

This level of protection ensures that internal electronics, sensors, and collected devices remain safe from rain, humidity, dirt, and temperature fluctuations. Additionally, UV-resistant coatings and weather-sealed enclosures help prevent degradation from prolonged sun exposure, making these machines suitable for long-term outdoor installation in plazas, parking lots, and transit hubs.

Q4: Do these machines offer any security features?

Absolutely. Security is a top priority for reverse vending machines, especially since they store valuable electronic devices. Key security features include:

• Locked Collection Bins: High-strength locking mechanisms secure the storage compartment, accessible only by authorized personnel.
• Anti-Tamper Alarms: Sensors detect unauthorized access attempts and can trigger alerts or notifications.
• Surveillance Integration: Many RVMs support camera integration for real-time monitoring and video recording.
• Secure Data Handling: Devices are often scanned and wiped of personal data immediately upon acceptance, ensuring user privacy and compliance with data protection regulations.

Together, these features protect both the collected e-waste and the integrity of the recycling process.

Q5: What types of locations are ideal for RVMs?

Reverse vending machines are most effective when placed in high-traffic areas with engaged audiences. Ideal deployment locations include:

• Retail Stores: Electronics retailers, supermarkets, and shopping malls offer natural foot traffic and customer engagement opportunities.
• Educational Institutions: Universities and colleges can promote sustainability among students and staff.
• Corporate Campuses: Businesses can support green initiatives and employee wellness programs through on-site recycling.
• Public Spaces: Train stations, airports, and city centers provide broad public access.
• Events and Festivals: Temporary installations at eco-events or tech expos can boost awareness and participation.

The choice of location depends on the target demographic and the goals of the recycling program—whether it's maximizing volume, raising awareness, or supporting corporate social responsibility.

Q6: How are user engagements increased in various locations with RVMs?

User engagement is significantly enhanced through incentive-based programs that make recycling both rewarding and meaningful. Common engagement strategies include:

• Instant Rewards: Users receive gift cards, store discounts, or mobile top-ups immediately after depositing a device.
• Loyalty Points: Integration with customer loyalty programs encourages repeat interactions and brand retention.
• Charitable Donations: Options to donate the value of the recycled phone to a cause resonate with socially conscious users.
• Interactive Displays: Touchscreens provide educational content about e-waste and show real-time impact metrics (e.g., CO₂ saved, resources recovered).
• Seasonal Campaigns: Limited-time promotions or challenges create urgency and boost participation rates.

These tactics not only increase recycling rates but also foster environmental awareness and strengthen community involvement.

Q7: Is the e-waste recycling process tracked by RVMs for mobile phones?

Yes, modern reverse vending machines are equipped with advanced tracking and monitoring capabilities, often powered by IoT (Internet of Things) technology. These systems enable real-time data collection on:

• Number of devices collected per day/week/month
• Types and conditions of phones recycled
• User demographics and drop-off patterns
• Machine performance and maintenance alerts

This data is invaluable for optimizing operations, measuring the success of recycling campaigns, and generating reports for sustainability goals. It also supports transparency by allowing organizations to share verifiable impact metrics with stakeholders, regulators, and the public.

Some RVM networks even integrate with blockchain or cloud platforms to ensure secure, tamper-proof tracking from collection to final processing, reinforcing trust in the e-waste recycling chain.