Types of telephone lines

There are several differences among telephone lines which are available for organisations. Sometimes it can become hard to know which telephone line is suitable for you, and what the line does. This article is a simple and easy guide to understand the different types of telephone lines including PSTN line, the Digital telephone lines and VoIP phone system.

PSTN line

PSTN stands for Public Switched Telephone Network. It is an analogue telephone network for business and residential clients in the United Kingdom. The analogue telephone lines are single phone lines which are mostly utilised for making calls, franking machines, connecting PDQ machines, fax machines and linking to a modem for the dial-up internet connection.

  • Incompatibility Problems

If your telephony and broadband share the same analogue phone line and your company needs more phone lines (using the same phone number) you will have to order multi-line phone service. But, your broadband service would be removed if a phone line is transformed into a multiline because of the ‘voice only’ nature of the service. In order to get around this, you will have to have a new single phone line installed for the broadband connection for operating on and upgrading the original single phone line to a multiline then after that is live, it allows you to keep your phone number on the original phone line by upgrading to the multiline.

PSTN Copper Lines

Often PSTN is also referred to as Plain Old Telephone System (POTS). This is a traditional copper network which is being slowly phased out with the introduction of NBN. Even though it is still in use by many businesses, PSTN phone lines are old technology that is being out-dated by the VoIP telephony. The PSTN lines do not need a phone system and are frequently used by the small businesses or as standalone lines for the fax, EFTPOS or delivery of DSL service.

The Digital telephone lines

There are two kinds of Digital telephone lines: the ISDN2e and the ISDN30e. The ISDN stands for the Integrated Services Digital Network and the e at the end is an abbreviation of the signalling standard called European Telecommunication Standards Institute (ETSI). This body is responsible for the technical standard in telecommunication in the European region.

Also Read: “8 Real IoT Applications In 2021


ISDN2e is actually a high-performance data and voice service. It is suitable for the smaller workplaces. A basic installation lets you connect almost eight digital devices and make two simultaneous calls. The ISDN2e is equivalent of 2 digital phone lines called channels which operate at 64kbps of speed. The 2 channels can work autonomously which allows you to make a call and use the internet and receive fax simultaneously. The ISDN2e line can provide up to 128 kbps of speed when the 2 channels are combined in order to connect to the internet connection, which is over twice as quick as the analogue modem.

Since the connection is digital, there is the extra advantage of amplified clarity for calls and bigger emails and data files can be received and sent more securely and quickly. If your company needs more connection in the future, then you can add more ISDN2e circuits to the existing installation which increases the number of concurrent connections and available data bandwidth. But it is more efficient for companies to take an ISDN30e channel if you require over six lines or you feel that you will require more lines down the line. Furthermore, there are two kinds of ISDN2e phone lines:

•           The ISDN2e Systems: these are quite like the ISDN30es. These have ranges of DDIs on them and SNDDIs. There are by far the more common of the 2 types of ISDN. The number of SNDDI and DID are limited to 5 ranges (including the main phone line if this isn’t part of a DID range).

•           The ISDN2e Standard: this has a maximum size of two channels and can’t be any larger than this. They don’t have Single Number Direct Dial In (SNDDI’s) OR Direct Dial In (DDI’s). rather they have Multiple Subscriber Numbers (MSNs). The ISDN2e standard is individual phone numbers which can be demanded and added to the line. They don’t come in blocks, only as single numbers. These are programmed into telephone systems in almost the same way as the SNDDIs on ISDN2 are.

  • ISDN30e: it is an improvement to the ISDN30 service. The ISDN30e is offered with the newest network software that allows you access to the supplementary services like; call forwarding of data and voice calls. The ISDN30e is an innovative digital solution for bigger organisations. It is an equivalent of thirty analogue lines which work at 64lpbs each. The use of fibre optic cables can provide great benefits for bigger companies as they are more reliable compared to the traditional copper wires. The ISDN30e is a high-performance data and voice service for contemporary businesses. Their digital technology provides high line quality which allows for:
  • Clear voice communication with other ISDN users
  • Rapid connection
  • Provides employees with the individual DID numbers
  • Ideal for the networks connecting two or more offices

The ISDN30e line offers the volume for between eight and thirty continuous calls. These voice calls can be both from individuals calling into a company or the voice calls which are made from the office to others. Every call which is made will need one channel. If your company requires over thirty channels, then you will have to order an extra ISDN30 line.

With the ISDN30e line, you get an unlimited amount of DID phone numbers, however, limited to 5 ranges, it allows your business and customers to directly dial through to employees’ members, without passing over a switchboard.

Business VoIP SIP Trunks

The business SIP trunks and the IP telephony are actually the new age business telephone lines. The Session Initiation Protocol (SIP) is a way to deliver phone services over the internet. In simple terms, the SIP trunks are basically business lines and it allows you to make and receive phone calls over the internet connection. Similarly, you can buy a block of in dial numbers which can be committed to the SIP trunk number, efficiently providing you a range of direct numbers that the outside callers can contact you on. Usually, they are assigned to individual PBX extensions so that the outside callers can directly call instead of going through the main phone number or the reception.

The IP telephony and SIP trunks need an IP phone to function and are a perfect substitute for the traditional telephony and the ISDN services. Recent enhancements in the broadband infrastructure and access to high-quality broadband services mean that companies can now take benefit of this highly flexible and powerful technology. If you wish to get VoIP phone services, then you should search for the UK VoIP providers.


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