What is a POTS Line? How Does It Work?

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A Plain Old Telephone Service (POTS) line, the traditional telephone service, has been a telecommunication mainstay for over a century. In POTS lines, voice data is transmitted via copper wires and analog signals.

Despite the rise of digital technologies like Voice over Internet Protocol (VoIP), POTS lines are valued for their reliability and simplicity, especially in scenarios where modern services are less effective.

Using POTS lines involves analog, circuit-switched technology with inherent speed, cost, and flexibility limitations. Conversely, adopting VoIP without understanding its digital, packet-switched nature and broadband dependency can lead to performance issues.

What is the POTS Line?

A Plain Old Telephone Service (POTS) line is the traditional analog telephone system that transmits voice over copper wires using circuit-switched technology. It supports essential functions like voice calls, faxing, and dial-up internet.

While digital solutions like VoIP offer more features and efficiency, POTS lines remain vital for their simplicity and dependability, particularly in areas with limited digital infrastructure and critical services like emergency communications.

History of POTS Line

The Plain Old Telephone Service (POTS) originated in the late 18th century. Initially, telephone lines connected only two parties directly. In the late 1800s and early 1900s, the system grew into a vast network managed by switchboards and operators, then became automated with rotary dial phones in the early 20th century.

The POTS line became the standard telephone service, utilizing analog technology and copper wires to transmit voice signals. Over the decades, this system connected millions of homes and businesses worldwide, forming the backbone of global communication before the advent of digital technology.

How Does POTS Line Work?

A Plain Old Telephone Line works by sending and receiving signals via wires. POTS has mostly stayed the same since the late 19th century and relies on analog signal technology and circuit-switching to facilitate voice communications. Over time, only their working methods have evolved.  The way copper and analog lines are used has stayed the same.

How Traditional Phone Lines Worked?

How traditional phone line works

Analog Signal Conversion: When a person dials a number into a POTS phone, each digit creates a series of electrical pulses converted into analog electrical signals.

Transmission Over Copper Wires: Signals are transmitted over copper wires connecting the caller's and recipient's phones. Connections are made between the local loop (the wiring between the home and exchange) and the central office (CO), where the call is routed.

Dedicated Circuit Establishment: The central office connects the caller and receiver using circuit-switching technology to make the call.

Ringing and Connection: The central office sends a ring signal to the recipient’s phone. The circuit completes once the recipient picks up, and the conversation can occur.

Voice Transmission: The analog signals are carried continuously over the established circuit, allowing real-time voice communication.

Call Termination: When one party hangs up, the circuit is broken, and the central office disconnects the line, ending the call.

How Modern Phone Line Works?

While maintaining the foundational principles of POTS, modern phone lines have integrated some digital elements to improve performance:

How modern phone line works


Dialing and Initial Processing: Modern phones convert dialed digits into digital signals, often using Dual-tone Multi-frequency (DTMF) signaling, which assigns each key a unique frequency pair.

Digital Conversion: An analog-to-digital converter (ADC) converts the user’s voice from analog sound waves into digital data packets and encodes them into digital bits.

Data Packetization & Compression: The digital data is then packaged into data packets, which include voice data and headers containing metadata about the data (like source, destination, and sequence information).

Voice data is often compressed using codecs (coder-decoders), which reduce the amount of data transmitted and required bandwidth while maintaining sound quality.

Routing: Packets are routed using dynamic routing protocols, enhancing efficiency while managing network congestion. Network equipment, such as switches, routers, and dedicated networks, is used for routing in today's systems.

Reconversion to Analog: Once the data packets reach the recipient’s phone, they are re-converted from digital back into analog signals using a Digital-to-Analog Converter (DAC).

Call Termination: When a user hangs up, a signal is sent across the network to terminate the call. Resources allocated to the call (such as bandwidth and circuits) are released, and dedicated circuits are disconnected.

Benefits of POTS Line

POTS lines provide consistent, high-quality voice transmission without needing a separate power source, even during power outages. Their universal compatibility also makes them a straightforward and secure choice for voice communications.

Below are some of the benefits of the POTS line:

Reliability: POTS lines are highly reliable, providing consistent service with minimal downtime. They continue to operate during power outages because they do not require external power.

Simplicity: These lines are straightforward to use. The technology is mature and well-understood, which simplifies troubleshooting and repair.

Universal Compatibility: POTS is compatible with a wide range of telephony equipment and is accessible virtually everywhere, ensuring consistent communication capabilities.

Secure Communication: Due to their direct physical connections, POTS lines offer a more secure channel for voice communications and are less susceptible to hacking or eavesdropping than internet-based communications.

Quality: They generally provide clear voice quality without latency or jitters, especially over short distances.

Drawbacks of POTS Line

A POTS line lacks the advanced features and flexibility of a modern digital communications system and requires high maintenance and operating costs. In addition, they are not scalable and can not provide businesses and individuals with integrated multimedia communication services.

Below are some of the drawbacks of the POTS line:

Limited Features: POTS lines lack the advanced features and functionalities that digital and VoIP systems offer, such as multimedia support, messaging, and video calls.

Higher Maintenance Cost: The aging infrastructure of copper lines can be expensive to maintain and repair, especially as fewer technicians specialize in POTS.

Lack of Scalability: Adding more lines often requires additional physical wiring, which can be cumbersome and expensive.

Cost: POTS lines typically have higher ongoing costs for long-distance and international calls than VoIP or digital communications.

Inflexibility: They are less flexible in supporting modern business needs like remote work, digital collaboration, and integrated communication platforms.

Is There Any Alternative to The POTS Line?

Yes. VoIP is a great alternative to a POTS line. VoIP converts your voice calls into digital signals that travel over your internet connection, often cheaper than POTS lines.  With VoIP, you can enjoy features like voicemail, call forwarding, and even video conferencing, making communication more efficient and flexible.

📝Read More: Understanding Different Types of VoIP Technology

POTS Line vs. VoIP: Key Difference

POTS lines use analog signals and copper wires for basic voice communication, and they are known for their reliability and simplicity. At the same time, VoIP technology sends voice as data packets over the Internet, offering advanced features, cost savings, and flexible usage across multiple devices and locations.

ParametersPOTS LineVoIP
Transmission method Uses a fixed or dedicated line to make a callUses an internet connection to make a call
Based onCircuit Switching Packet Switching
Cost Higher maintenance and call costsLower operational and setup costs
SignalConvert voice into electrical signal Convert voice into a digital signal
FlexibilityFixed locations, limited scalabilityFlexible usage across devices and locations
FeaturesBasic voice communication, with call forwarding, call transferring Aside from call forwarding and call transferring, other advanced features include video calls, call queueing, call recording, and virtual numbers
Charge No free PSTN to PSTN calls Free VoIP to VoIP calls 
IntegrationLimited to basic phone functionsIntegrates with other digital services (CRM, cloud, etc.)
Deployment ProcessSlower, requires physical setupFast, can be deployed remotely
Multimedia Does not support multimedia transmissions like audio, video, and any other multimedia.Supports multimedia transmissions like audio, video, and any other multimedia.
Scalability    Difficult and costly to scaleEasy to scale without significant infrastructure

Who Should Use POTS?

  1. Businesses with Critical Dependability Needs: The POTS Line does not require external power or the internet, making it a vital feature in emergency services and hospitals.
  2. Areas with Limited Internet Connectivity: POTS lines can benefit rural or remote locations with unreliable or unavailable internet service.
  3. Users Needing Simple Voice Services: For those who prefer simplicity, the POTS service offers a familiar, straightforward service without the need to learn new technologies.

Who Should Use VoIP?

  1. Businesses Looking for Cost Savings and Flexibility: Businesses of all sizes, whether startups or large corporations, can benefit from VoIP's reduced operational costs. Adding or removing lines is simple with VoIP systems.
  2. Businesses Requiring Advanced Features: VoIP supports advanced features not available with POTS, such as video calls, messaging, virtual meetings, and integration with digital business tools, which are essential for modern enterprises.
  3. Businesses with Global Operations: VoIP offers significant advantages for international calling and communications, including lower costs, no need for country-specific infrastructure, and unified communication across global offices.
  4. Users Seeking Integration with Other Technologies: VoIP enables integration with other business applications, such as CRM systems, by providing APIs and software compatibility.

Frequently Asked Questions

What are the main cost differences between VoIP and POTS lines?

VoIP offers lower monthly rates and cheaper long-distance and international calls than POTS. Due to traditional copper lines and older technology, POTS lines have higher maintenance, infrastructure, and call costs.

How do VoIP and POTS lines differ in installation and maintenance?

VoIP systems are easier and cheaper to install and maintain because they use existing internet infrastructure and can be managed virtually. POTS lines require physical copper wires and are costly to install and maintain.

Can VoIP work during a power outage like a POTS line?

Unlike POTS lines, VoIP requires power for the devices and internet service. However, solutions like Uninterruptible Power Supplies (UPS) and mobile VoIP apps can help mitigate this issue.

Which system is better for businesses that need advanced communication features?

VoIP is the superior choice for businesses that require advanced features such as video conferencing, instant messaging, mobile apps, and integration with business software like CRM systems. POTS lines are limited to basic voice communication.

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