Plain old telephone service is one of the most reliable communication channels we have—with more than 13.5 billion calls being made every day.
The Public Switched Telephone Network (PSTN) has been used for over 100 years to route and connect voice calls. Initially, Integrated Services Digital Networks (ISDNs) became an early digital transmission solution that improved voice quality and speeds over traditional telephone networks.
But times are changing. Alternatives like broadband telephony and Voice over Internet Protocol (VoIP) have revolutionized communication, offering lower infrastructure costs and advanced features like unified communications and app integrations.
While PSTN has played a critical role in connecting people—it’s important to understand how it works, its strengths, and why modern alternatives are becoming the preferred choice for businesses and individuals.
Let’s explore the fundamentals of PSTN, its mechanisms, and what the future of communication technology looks like.
What is the PSTN—and how does it work?
PSTN, often referred to as the traditional telephone network or plain old telephone service (POTS), operates using circuit-switched technology.
This means a dedicated communication path is established for the duration of each call, ensuring reliable and high-quality voice connections.
However, POTS represents the legacy infrastructure of the PSTN and is considered outdated in today’s tech-savvy environment due to its limitations in scalability, flexibility, and integration with modern digital communication technologies.
PSTN architecture and components
The Public Switched Telephone Network (PSTN) architecture is a marvel of engineering, designed to provide reliable and efficient voice communication services across the globe.
This intricate system comprises several key components, each playing a vital role in ensuring seamless connectivity. These components include:
Local Exchanges: Also known as a central office, the local exchange is the heart of the PSTN in any given area. It connects subscribers within a specific geographic region and routes their calls to the appropriate destinations. This component is crucial for managing the flow of communication within local telephone networks.
Switching Centers: These are the backbone of the PSTN. Switching centers are responsible for routing calls between different local exchanges. They ensure calls are efficiently connected to their intended recipients, whether they are across town, the country, or somewhere else in the world.
Telephone Lines: The physical connections that carry voice data between subscribers and the local exchange in a traditional telephone system. These lines can be made of copper wires, fiber optic cables, or a combination of both, each offering varying levels of speed and reliability.
Fiber Optic Cables: Used to transmit voice signals between switching centers and local exchanges. Fiber optic cables are known for their high-speed data transmission capabilities and resistance to interference. They are a critical component in modernizing traditional telephone networks.
Cellular Networks: In addition to landlines, the PSTN also integrates with cellular networks to provide mobile phone services. These networks consist of cell towers that transmit and receive voice data packets to and from mobile devices, expanding the reach of the PSTN.
Satellites: For remote areas where traditional infrastructure is not feasible, satellites play a crucial role. They transmit and receive voice signals to and from satellite phones, ensuring that even the most isolated locations can stay connected and connect with traditional phone systems.
How the calling process works
The traditional telephone system seems fairly straight forward on the surface. However, there are a variety of technologies that enable seamless calling between analog and digital devices.
Here is a simple breakdown of how the process works today:
Sound Conversion: When you dial a number for phone calls, your telephone converts sound waves into electrical signals. VoIP redefines phone calls by allowing voice communication to be transmitted over the Internet, making calls more flexible and cost-effective compared to traditional landline systems.
Transmission to Local Exchange: These signals are transmitted through copper cables to a terminal, which is then routed to a local exchange or central office.
Signal Routing: From the exchange, the signals travel through a network of fiber optic cables, converting electrical signals into light pulses for faster transmission.
Delivery to Final Destination: The signals reach their destination, where they’re converted back into sound waves for the recipient.
Despite the complexity of the infrastructure, this process takes only a few seconds.
Popular PSTN services and features
The Public Switched Telephone Network (PSTN) offers a variety of services and features that have been the cornerstone of reliable voice communication for decades.
These services ensure that users can communicate effectively, whether they are making a local call or connecting with someone halfway around the world.
Today’s businesses rely on advanced features when making telephone calls to support their employee and customer needs. These include:
Voice Calls: At its core, the PSTN enables voice calls between subscribers. This service is the foundation of the telephone network, allowing people to communicate clearly and reliably.
International Calls: One of the standout features of the PSTN is its ability to facilitate international calls. This service allows subscribers to connect with individuals in other countries, making the world a smaller place.
Local Exchange Services: The PSTN provides local exchange services, enabling subscribers to make calls within their local area. This service is essential for everyday communication within communities.
Call Forwarding: The PSTN offers call forwarding services, allowing subscribers to redirect incoming calls to another phone number. This feature is particularly useful for ensuring that important calls are not missed.
Call Waiting: With call waiting services, subscribers can receive incoming calls even while they are already on another call. This feature ensures that users do not miss important communications.
Conference Calling: The PSTN enables conference calling, allowing multiple subscribers to participate in a single call. This feature is invaluable for business meetings and group discussions.
Speed Dial: Allows a subscriber to program frequently dialed numbers into short code sequences (e.g., #1, #2, etc.), so they can be called quickly.
Voicemail: When a call goes unanswered, the caller can leave a recorded message in a voice mailbox. Users can retrieve messages locally (via the handset) or remotely (dialing into the mailbox).
Caller ID: Displays the incoming caller’s phone number (and sometimes name) on a Caller ID-capable phone or device before the call is answered.
The backbone of PSTN: Switching technology
Switched telephone networks are the core of PSTN, enabling efficient routing and connection of calls. However, the costs associated with the PSTN phone system can be significant, particularly when scaling for multiple employees, making it less attractive for businesses compared to modern VoIP services.
Switched telephone networks use four main types of switches:
Local Exchange: Handles up to 10,000 telephone lines in a specific area and routes calls to their destination using unique phone numbers.
Tandem Office: Manages connections between local exchanges within the same city, routing calls closer to their final destination.
Toll Office: Facilitates long-distance, national calls by connecting tandem offices.
International Gateway: Handles global call switching, enabling seamless international communication.
What is the cost of the plain old telephone service?
The cost of using a Public Switched Telephone Network (PSTN) can vary widely based on several factors, including the type of service, location, and provider.
For residential users, basic PSTN service typically ranges from $20 to $50 per month. This basic service often includes local calls, but additional fees may apply for long-distance and international calls and for features like call waiting and caller ID.
For businesses, the costs are generally higher, with basic PSTN service ranging from $50 to $100 per month. Businesses often require additional features such as call forwarding, conference calling, and voicemail, which can incur extra charges. Installation fees also vary, with residential installations costing between $50 and $200, while business installations can range from $100 to $500.
International calls can be particularly costly, with rates ranging from $0.10 to $1.00 per minute, depending on the destination country and the provider. These costs can add up quickly, especially for businesses with high call volumes or multiple lines.
It’s important for users to carefully consider these costs and compare them with modern alternatives like cloud voice or Microsoft Teams Operator Connect, which often offer more cost-effective solutions for international communication.
PSTN telephone service applications and industries
The Public Switched Telephone Network (PSTN) has a wide range of applications across various industries, making it a versatile and essential communication tool.
Healthcare: PSTN is used for medical consultations, patient communication, and emergency services, ensuring that critical information is transmitted reliably and securely.
Financial Services: PSTN is crucial for secure transactions, customer service, and the transmission of financial data.
Education: Another industry that heavily relies on PSTN for online learning, remote classrooms, and administrative communication, facilitating seamless interaction between students, teachers, and administrative staff.
Government Agencies: Use PSTN for emergency services, public safety, and internal communication, ensuring that essential services remain operational even during crises.
Retail: PSTN supports customer service, sales, and marketing efforts, helping businesses maintain strong connections with their customers.
Other industries like hospitality, transportation, and manufacturing also benefit from the reliability and reach of PSTN, using it for various communication needs that are critical to their operations.
How reliable and secure is the PSTN?
The Public Switched Telephone Network (PSTN) is renowned for its security and reliability, making it a trusted choice for voice communication.
One of the key security features of PSTN is encryption, which helps prevent eavesdropping and interception of calls. This ensures that sensitive information remains confidential during transmission.
Authentication protocols are another important security measure, verifying the identity of callers and preventing unauthorized access to the network. PSTN providers also implement redundancy in their networks, with backup systems and power sources in place to ensure continuous service during outages.
Quality of Service (QoS) is a priority for PSTN providers, who prioritize voice traffic to ensure high-quality calls with minimal latency. However, PSTN is not immune to security threats. Toll fraud, where hackers exploit vulnerabilities to make unauthorized calls, is a significant concern. Eavesdropping, where hackers intercept and listen to calls, and Denial of Service (DoS) attacks, which overwhelm the network with traffic, are other potential threats.
Despite these challenges, the robust security measures in place make PSTN a reliable choice for secure voice communication.
Current challenges and the future of PSTN
The Public Switched Telephone Network (PSTN) has been a reliable communication system for decades, but it faces several challenges in the modern era.
Understanding these challenges and the potential future of PSTN is crucial for navigating the evolving landscape of communication technology. Notable challenges include:
Declining Revenue: With the rise of Voice over Internet Protocol (VoIP) and other internet-based communication services, the PSTN is experiencing declining revenue. These modern alternatives offer cost-effective solutions that are increasingly preferred by businesses and individuals.
Limited Adaptability: The circuit-switching technology that underpins the PSTN limits its adaptability to modern communication needs, such as data services and multimedia communication. This limitation makes it less suitable for the demands of today’s digital world.
Integration with VoIP: Despite its challenges, the PSTN can integrate with VoIP and other technologies to create hybrid systems. These systems leverage the strengths of both traditional and modern communication methods, offering tailored solutions for specific needs.
Maintenance and Upgrades: Maintaining and upgrading the PSTN infrastructure is an ongoing challenge. Regular maintenance is required to ensure reliability and efficiency, but these efforts can be costly and labor-intensive.
Future Prospects: While the future of the PSTN is uncertain, it may continue to play a crucial role in certain areas. For example, it remains essential for emergency services, rural areas with limited internet access, and network interoperability. However, as technology continues to advance, the PSTN may eventually be replaced by more modern communication systems.
By understanding these challenges and the potential future of the PSTN, businesses and individuals can make informed decisions about their communication needs and explore the benefits of modern alternatives like VoIP.
Popular alternatives to PSTN
While PSTN has served the world well, its limitations have paved the way for modern communication systems.
Internet telephony transmits voice over the internet, offering numerous advantages when compared to traditional telephony.
The technology behind PSTN remains largely unchanged since the last century, and maintaining this infrastructure is costly.
IP telephony, a cost-effective and scalable solution for businesses, provides advanced features and efficiency.
This has led to the rise of VoIP (Voice over Internet Protocol) and modern cloud voice solutions, which have become a game-changer for communication.
Key benefits of VoIP over PSTN
Cost-Effective: Significantly cheaper, especially for international calls, as it utilizes internet infrastructure compared to the traditional PSTN phone system.
Advanced Features: Offers capabilities like call forwarding, voicemail-to-email, and video conferencing.
Scalability: Easy to scale as businesses grow, unlike PSTN, which requires new physical lines.
Flexibility: Allows calls from any internet-connected device, unlike PSTN’s reliance on landlines.
PSTN vs. VoIP: A quick comparison
What makes VoIP and modern cloud calling a better choice over traditional PSTN calling? See a detailed breakdown below:
| Feature | PSTN | VoIP |
|---|---|---|
| Technology | Circuit-switched telephone service | Packet-switched (internet-based) telephone service |
| Cost | Higher due to infrastructure needs | Lower, leveraging existing internet |
| Flexibility | Limited to landlines | Supports multiple devices |
| Features | Basic voice calls | Advanced (e.g., video conferencing) |
| Scalability | Requires physical infrastructure | Easily scalable via software |
| Quality | Consistent | Depends on internet speed |
Technology
PSTN: Circuit-switched telephone service
VoIP: Packet-switched (internet-based) telephone service
Cost
PSTN: Higher due to infrastructure needs
VoIP: Lower, leveraging existing internet
Flexibility
PSTN: Limited to landlines
VoIP: Supports multiple devices
Features
PSTN: Basic voice calls
VoIP: Advanced (e.g., video conferencing)
Scalability
PSTN: Requires physical infrastructure
VoIP: Easily scalable via software
Quality
PSTN: Consistent
VoIP: Depends on internet speed
PSTN maintenance and troubleshooting
Maintaining and troubleshooting the Public Switched Telephone Network (PSTN) involves several critical steps to ensure the network operates smoothly and efficiently.
Regular maintenance is essential, with providers performing tasks such as software updates and hardware checks to prevent issues before they arise. When problems do occur, PSTN providers use specialized tools and techniques to identify and resolve issues.
Common issues include call drops, poor call quality, busy signals, and the absence of a dial tone. Providers monitor the network in real-time to detect and address these issues promptly, minimizing disruptions to service.
Customer support is a vital component of PSTN maintenance, with providers offering assistance to help users troubleshoot and resolve problems. By following these steps, PSTN providers can ensure the network remains reliable and users can enjoy high-quality voice communication.
While PSTN has its challenges, its robust maintenance and troubleshooting processes help maintain its reliability and efficiency, ensuring it continues to serve as a dependable communication tool.
Discover the best way to achieve PSTN connectivity
PSTN has been an essential tool in global communication for decades, but it’s no longer equipped to meet the demands of modern businesses.
Alternatives like VoIP, cloud calling, and other Internet-based telephony systems are cost-effective, scalable, and loaded with advanced features that support today’s dynamic workplaces.
Are you looking to future-proof your voice systems? Contact us today to explore your options for achieving future-proofed PSTN connectivity.
