Traditional T1 line service comes in a number of flavors. The original implementation for the telephone industry consists of 24 channels of digitized telephone service on two pair of twisted copper phone wires. A device called a channel bank converts the multiplexed digital signal to and from 24 individual analog business phone lines.
A more popular version of the T1 telephone line is called ISDN PRI. It’s very popular with companies that have their own in-house PBX telephone system. With ISDN PRI, you get 23 outside lines plus a switching and data channel that speeds up connections and provides Caller ID for the phones.
Yet another implementation of T1 is the T1 data line. This version supplies point to point data connections between business locations or dedicated Internet access. The bandwidth is 1.5 Mbps for a single T1 line, but multiple lines can be bonded together to increase bandwidth to as high as 10 or 12 Mbps.
Most companies have a T1 line for data or Internet access plus separate telephone service, or one T1 for broadband Internet and a separate ISDN PRI to run the phone system. Smaller companies don’t get involved with multiple T1 lines because they only have a few office phones and don’t need 23 outside lines. They simply pay one phone bill for the number of business lines they have and a separate bill for their T1 service.
An option that may work just as well and save small businesses money is to have both the telephone service and Internet broadband on the very same T1 line. A conventional T1 line isn't intended to do this. It is set up to work as a telephone trunk line or a high speed data line. The configurations aren’t interchangeable. However, there is another flavor of T1 service that does provide the dual function of voice with data.
The traditional name for this service is Integrated T1. The latest offerings are called SIP trunking or SIP trunking with Internet.
What’s the difference? Actually, they are more alike than different. The way it works is that the service provider installs a device called an IAD or Integrated Access Device at each end of the T1 line. This device combines voice and data by converting them to a common protocol, which happens to be IP packets. Once in packet format, the IAD can manage line bandwidth to ensure that voice packets have priority over data packets so that telephone call quality is maintained no matter what sort of Internet activity is taking place.
Line bandwidth is shared. If there are no calls in progress, all 1.5 Mbps is used for broadband Internet. When a phone is picked up, bandwidth for that call, typically 90 Kbps or less, is reserved for that call. The rest is still used for the Internet. Note that the phone calls don’t actually go over the Internet. They simply share the T1 line connection to the service provider. The more calls that are simultaneous in progress, the more bandwidth is reserved for voice packets and the bandwidth for Internet access is proportionally reduced.
This process is sometimes called dynamic T1 or dynamic line service to reflect that the proportioning between voice and data is handled automatically. So, where does SIP trunking come in?
SIP is the switching protocol for VoIP phones. SIP trunking is a process of providing public phone system lines to a VoIP telephone system using the native Session Initiation Protocol. A SIP trunk will connect directly to your IP PBX for IP phones. It can also be configured to offer an analog handoff so you can use the analog business phones you have now.
What’s exciting about SIP Trunking and Internet on a T1 line is that it can often be less expensive than buying a T1 line and phone service separately. One company that specializes in this product is Vocal IP Networx. They can save you money by providing a single telecom bill each month at a cost that may well be less than what you pay now for the same quality of service.
Do you suspect that you might save money by consolidating your telephone and Internet service with one provider? If so, get competitive pricing for SIP Trunking and Internet on a T1 line and similar services and see if this option makes sense for you.