Many businesses just assume a landline is a landline…until they go for one.
Regular business landlines come in two flavors: PSTN and ISDN. (We’ll leave VoIP aside for now, and talk about that another day.)
Both systems have their pros and cons, and the ideal solution for your business may well be to use a combination of the two.
PSTN (Public Switched Telephone Network)
PSTN, which is also called POTS (Plain Old Telephone System), provides a single telephone line with a single telephone number.
This service is ideal for smaller businesses that require only one or two lines. It is also recommended for many services where a dedicated line is required, such as fax and EFTPOS machines, return-to-base alarm systems, and ADSL connections.
ISDN (Integrated Services Digital Network)
ISDN digital service provides multiple channels per line and allows for multiple simultaneous phone calls. Each digital line can carry voice and data services. These lines provide higher bandwidth than PSTN lines, making them ideal for services including data transfer and video conferencing.
This service is ideal for medium to large businesses and typically connects to office phones through a PBX system.
For most businesses, only 30-40% of their phone lines are in use at any given time. That means that in an office with 10 employees where everyone has their own phone, you would need 10 PSTN lines or 4 ISDN lines. This helps make ISDN cost effective, especially in larger offices.
- ISDN 2
- This is the entry level for ISDN, which provides two channels on your ISDN line. As your business grows, this service can be expanded to 4, 6, then 8 channels.
- ISDN 10, 20, 30
- Larger companies can subscribe to 10, 20 or 30 ISDN channels. Services are easily upgraded from 10 to 20 or 30. If you need more than 30 channels, a second ISDN service can be installed.
With ISDN, each phone within your company can have a unique phone number, which people outside the company can dial directly. (This is called a DID or Direct In-Dial number.) You can usually buy DID numbers in blocks of 100 from your telco. When you buy a block of numbers this way, they remain yours and you can take them with you if you ever decide to switch to a different provider.
Which one is right for your business?
For medium and large businesses, an ISDN system for your telephone lines will help you save money (remember that you need 60-70% fewer lines than a comparable PSTN system).
Before going all the way with ISDN, it’s important to consider the dedicated services you want to run. For example, services like ADSL and some back-to-base alarm systems are incompatible with ISDN. (If you’re not sure what types of lines your services support, it’s a good idea to check with your providers.)
Therefore, the best solution for many medium and large companies is to use ISDN for their telephone lines, in addition to obtaining some PSTN lines for independent services.
Smaller businesses will often pay the same for an ISDN solution as a PSTN solution. The primary consideration here is the expected future growth for the business. The more phone lines you need, the more cost-effective ISDN becomes, so if the business is likely to grow quickly, it’s probably more cost-effective to start with an ISDN 2 system.
Check with your telecommunications company if you have any questions about which service is right for you. Most telecommunications companies are happy to provide advice without obligation.