Last Updated on January 28, 2026

Understanding how data travels across telecommunications networks is essential for any company manager to make technological decisions for their business. Circuit-switching and packet-switching are the two fundamental technologies to understand. Both technologies enable telecommunications, however; they accomplish this utilizing different methods.

This article will discuss the concepts of circuit-switching and packet-switching in both Public Switched Telephone Network (PSTN) and packet-switched networks.

What is the Public Switched Telephone Network?

PSTN, also known as the Plain Old Telephone Service (POTS), is the traditional telephone system that is utilized worldwide. It consists of physically wired systems forming a network to enable individuals to create and receive phone calls. PSTN equipment includes telephone lines, fiber optic cables, cell networks, communication satellites, and undersea cables that are all interconnected through switching centers to route calls to their destination. Learn more about what is PSTN.

What is Circuit Switching?

Circuit switching is a method of data transfer used in telecommunications to join two nodes within a network and establish a dedicated connection. This is known as a communications channel or a circuit. The circuit remains connected for the entire duration of the communication session and guarantees full bandwidth of the channel. The circuit behaves as if the nodes were connected physically to ensure consistent service without interruption.

How does Circuit Switching work?

There are three phases of Circuit Switching.

1. Establishment of a connection: When a call is initiated, a dedicated connection is established between the caller and recipient. This is referred to as a circuit is established. This circuit remains established for the entire duration of the call even at moments when there is no communication or data transmitted.
2. Continuous connection: The associated resources, such as bandwidth, are reserved for the duration of the call when a circuit is created. This ensures call quality remains constant and in real time with no delays. The circuit remains open exclusively for the two parties involved in the connection. Nothing else can use the same circuit until the connection is terminated.
3. Termination: The circuit and all associated resources are released for other users when the connection is terminated.

Advantages of Circuit Switching

• Low Latency: Circuit switching establishes a dedicated connection which means there is little delay or lost packets in the transfer of data.
• Consistent Performance: There are no other resources competing for bandwidth because circuit switching utilizes a reserved connection. This provides steady performance for the entire duration of the call.
• Real time communication: Circuit switching is ideal for real time communication due to consistent performance and low latency for voice and video.

Disadvantages of Circuit Switching

• Inefficient use of resources: A dedicated circuit does not allow any data to be transferred over the line other than the parties involved in the communication. This means there is no utilization when the circuit has been established, and the parties are not communicating.
• Limited Scalability: Circuit switching requires physical lines to establish a connection. Additional circuits must be established to connect multiple simultaneous calls.
• Limited Flexibility: Circuit switching establishes a connection between two parties. The call is lost if the connection is disrupted and a new circuit must be established.

What is Packet Switching?

Packet switching is a method of sending data over digital networks. This method is used in telecommunications where data is grouped into short messages within a fixed format referred to as packets. The packets consist of both a header, to direct the packet to the destination, and a payload, the actual intended message that is extracted. A series of packets travel through the digital network to arrive at the destination. Each packet may take different routes through the network to reach the destination.

How does Packet Switching work?

There are three phases of Packet Switching.

1. Data Segmentation: The voice data is divided into packets. Each packet contains a portion of the message in the payload and destination addresses, sequence, and error codes in the header.
2. Routing: Each packet tries to find the best path through the network to the destination when they are sent. The packets may split up and move from one network to another to arrive at the destination.
3. Reassembly: The data packets are received, reassembled, and sent to the next location when they reach a hardware component in the network. This process is repeated throughout the journey through the network until the data packets reach their destination.

Advantages of Packet Switching

• Efficient: Packet switching resource paths are shared among multiple users and allocated when data is transmitted. It adapts to traffic patterns and bandwidth dynamically.
• Scalable: Packet switching allows devices to be added or removed easily without changes to the network.
• Resilient: Packet switching can operate at varying bandwidths and support a wide range of packet sizes. Packets can reroute via alternative paths if a network router or a node fails to ensure continuity. Dropped or missing packets can be resent by the sender to mitigate packet loss.

Disadvantages of Packet Switching

Quality of Service (QoS) may be impacted on a packet switching environment for several reasons:

• Latency: Packets travel through different routes of the network and with varying levels of speed due to congestion.
• Lost Packets: Some packets can be dropped or lost and unable to be resent.
• Limited Resources: Packets may arrive at their destination out of order and require processing to set the packets in the correct order. This may require additional resources.

Circuit-Switching vs. Packet-Switching

PRI Pros and Cons

Feature	Circuit Switching	Packet Switching
Usage	PSTN	VoIP, Mobile Data
Connection Type	Dedicated physical path	Shared, dynamic paths
Scalability	Limited	High
Latency	Low	High (Dependent up traffic)
Quality of Service (QoS)	High (Well suited for Real Time communication)	Limited (Dependent upon bandwidth)

How to record calls in both Circuit and Packet Switching environments

Telephone communication utilizes either Circuit Switching or Packet Switching. These technologies form the backbone of voice and data transmission. Calls transmitted over these systems can be recorded.

Recording calls on Circuit Switching and Packet Switching environments

Circuit Switching is utilized in PSTN lines leveraging T1, E1, T1 ISDN PRI and E1 ISDN PRI interfaces. Packet Switching is utilized in Voice over Internet Protocol (VoIP). Versadial’s call recording software is well suited for both environments and may record calls in many common call recording scenarios

Example: Call Recording Scenario #3

Multiple phones lines are connected to a company’s PBX or phone system in this scenario. The VSLogger Recording Server is connected between the PBX or phone system and the trunk. The VSLogger is connected to a network switch with a Mirror Switched Port Analyzer (SPAN) in a VoIP environment. The trunk may be a SIP, VoIP, or PSTN. The SIP/VoIP trunk utilizes Packet Switching while the PSTN trunk utilizes Circuit Switching. The recording method is passive, meaning the recording device does not actively participate in the call. This is one of many different call recording scenarios. You may explore other call recording scenarios if this does not fit your business environment or needs. Please contact us for additional information if you are interested in deploying call recording for your company and we will find the call recording scenario to best fit the needs of your business.

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Last Updated on January 28, 2026