How Does a PBX System Connect With The Outside World?

PBX systems are at the heart of any successful business. Communication is the most important aspect of building client relationships and conducting day-to-day business. Without an efficiently operating phone system, a business could lose revenue as well as client confidence.

Phone systems are designed to handle call volume that exceeds what one would normally see in a home. Since multiple calls are coming in at the same time, a phone system is essential to route these calls to the appropriate party where the customer doesn’t hear a busy signal. This is done through the use of circuits or multiple phone lines that are connected to the phone system. Based on call volume, these “phone lines” can either be an ISDN line, or could be a series of single lines. The choice of circuit is largely dependent on the expected call volume and budget of the business owner.

In cases of smaller businesses, using multiple single lines might make more sense. However, some may be surprised to find that the cost of one ISDN circuit might be less expensive than continually adding phone lines to keep up with demand. This is where projected growth should be considered when ordering circuits or phone lines. This is particularly true in cases where rapid growth is expected.

Referred to as a circuit, an ISDN is a type of “phone line” that has 24 channels with one channel being reserved for data such as caller ID. The remaining 23 channels can carry one call each simultaneously. This solution would work better than 23 individual phone lines to accommodate incoming and outgoing phone calls. These circuits can be set up in a PBX system to allow incoming or outgoing calls or a combination of both. Additionally, depending on the phone company used, they can be specified for either local or long distance. In most cases, they will be set up for least cost routing. You might be able to send both local and long distance calls over the same circuit, but it might not be cost-effective to do so.

ISDN T1’s, or circuits, are appropriate for larger businesses with a high expected call volume. These circuits are commonly seen in call center environments which have additional technology to route calls to agents. For companies having extremely high call volume, a DS3 is often used which is comprised of 28 T1’s or individual circuits. This allows for an even greater amount of call volume and might be a more cost-effective solution than ordering 28 individual T1’s. The cost of a DS3 will depend on the distance from the business location to the end of the carrier network. This is why it’s a good idea to shop around when considering purchasing a DS3 for communications. This way you can choose a carrier that has the shortest distance to minimize cost.

Another solution that is fast growing in popularity because of its versatility as well as cost savings is VoIP. Unlike the communications described above, VoIP technology transmits the conversation using IP technology in much the same way that a computer transmits data. Since both voice and data can reside on the same circuit, the need for the number of circuits can be minimized. Since VoIP converts the conversation to data packets, it’s important that the voice data not conflict with the normal transmission of data as seen when transferring files or sending email. This is because voice data must be received in the order in which it is sent. If the end of the conversation gets to the destination before the beginning, the conversation won’t be understandable. In the case of data transmission, if there’s a bottleneck, the network will simply begin sending the data again once the bottleneck clears.

Since conversations are real time, this won’t work for voice traffic. This is why it’s imperative to have the proper configuration in place to insure that the voice conversation always has priority. The number of calls that could run concurrently would largely depend on the size of the network, the data circuits and how much other data would be transmitted over the same circuit. Additionally, the network configuration plays a large role in the quality of the audio during a phone call. VoIP is appropriate for large and small businesses because of its scalability. Depending on the needs of the business, bandwidth can be moved up or down and allows the business to leverage the data network to route phone calls.

There are many solutions when it comes to connecting a PBX system to the outside world. Varying in cost and capacity, each solution has its benefits and drawbacks depending on customer need. Also a deciding factor is the PBX itself. Knowing what the PBX is compatible with as well as the expected call volume will go a long way in making the appropriate telecom choices to meet business needs.