Analog Phone Lines, Digital Phone Lines and VOIP (Voice Over Internet Protocol)
My name is Dennis Jenkins and I am in the interconnect business. This is the area of communications that connects the telephone to the telephone system which connects to the outside lines. This allows us to make telephone calls outside of the business or residence as well as extension to extension. The natural evolution of that is to also create conference calls that more than two people talk at the same time.
The telephone in its inception allowed for two or more parties to talk on a common path or “speech path”. For many years the form of telephony was a “party line” where the number of rings indicated the intended party to answer. As time went on “private lines” became the norm and if if your phone rang it was only for you. Another important feature of the private line is everyone else that use to be on your party line no longer had access to your conversations. Now if you want someone on your call, you conference them in.
The early private lines were the cord board made popular with “one ringy dingy, two ringy dingy” skit done a few years ago. This depicts the “routing” sequence of a manual PBX or Private Branch Exchange. This was also analog protocol as the voice was changed to the sine waves like on the oscilloscope of the “outer limits” TV show. Similar demonstrations of Sine wave activity are the equipment on the hospital shows showing the heart beating until it Flat Lines for the victim. Analog lines are still used for many items such as fax and modems.
As phone systems evolved, the need to manage more concurrent telephone calls strained the “speech Path” technology. The digital PBX came to market and allowed for more concurrent calls and “non blocking” systems. They were supporting T1 circuits. T1 circuits are a Digital circuit able to support 24 phone calls concurrently. These required cleaner transmission than analog and quickly became the “clear signal” promoted by dial tone providers and interconnect companies alike. It improved quality of conversation and brought to it another technology called DID. DID or Direct Inward Dial previously lived on dedicated circuits, but now were a part of the features of the T1. What this means is that of the 24 channels in the t1, all were available to share the task of calling the “company phone number” as well as Direct Inward Dial pointed at a specific desk or group. A group using a DID might be Customer Service, Technical Support, Human Resources or Accounting. More flexibility for the circuit means more services to the end user as well as his customers. Digital PBX systems continued to grow supporting multiple T1 circuits to support the larger business environment.
At this place in our timeline we have both Digital and analog sets working in our phone systems as well as Digital and Analog outside lines. Something that is growing in popularity is the internet. It is allowing us to communicate information quickly. We use email and instant messenger to chat with business colleagues and friends alike. It seems logical that if we can send messages, why shouldn’t we send voice. The protocol we use to communicate on the internet is TCP/IP or Transmission Control Protocol/Internet Protocol. The concise expression has evolved to IP, so the idea of talking on the internet has been coined VOIP or Voice Over Internet Protocol. VOIP starts with a phone set able to convert the voice to an internet protocol and in the environment of most businesses; the information is placed on the LAN or Local Area Network. The LAN is an area that is not part of the Internet, but rather inside the company. Much like a call from one desk to another is called an INTERCOM CALL, a message from a desktop to another desktop in the company could be referred to as a LAN CALL. An extension number, 101, calls another extension number, 102 on the same network just like a desktop, 192.168.1.101 calls another desktop 192.168.1.102. Both of these calls are internal or not using an outside line. In this example, the internet is like and outside line.
When I ask that question what is VOIP, frequently the answer is voice over the internet. A more accurate description is voice over LAN because most of the time, it will go to the LAN and then put out over analog trunks or Digital trunks (T1 or PRI). Most systems do not put voice over the internet. When they do, they have to implement some protocols to assure the voice packets get priority to maintain clarity of speech. If packets are lost or delayed, portions of the conversation are lost or delayed. A good example of this is we sometimes get intermittent conversations on our cell phones or brief interruptions in our television programming when packets or bits of information are lost. Because we have come from analog to digital where there is no interference by other packets or bits on the line, we are less tolerant of good communications. With the quantity of calls now handled by cellphones we experience the “breaking up” of conversations more than we did before cellphones were as popular as they are. Properly engineered VPN circuits can provide very good service with internet connectivity for workers who work from home or a remote office.
Because most VOIP systems add load to your LAN, it is also an area of concern to prioritize the packet traffic on your LAN when you upgrade to VOIP systems if you have heavy loads on your LAN. Much of the new computer hardware is gigabit compared to 100 megabit speeds which will help minimize the percentage of load added to the LAN as VOIP traffic joins the data traffic of your LAN.
VOIP (Voice Over Internet Protocol) Explained
VOIP is a word we frequently hear when we are talking about the current generation of business telephones. In some cases, we hear this expression applied to business and home solutions like Vonage and Skype. On occasion, I ask people what voip is and I usually get the answer “talking over the internet”. While talking over the internet is using voip, voip is also more commonly used without ever touching the internet. Voip represents the words Voice Over Internet Protocol.
OK! What does that mean?
Think of it this way, today as we drive down the road, we see gasoline powered cars, electric powered cars and diesel powered cars. Three different forms of energy to get the car to move down the highway. Ultimately the purpose is the same but in their own right, they are different. In the communication world, we use different protocols to send words down the communication highway. Three examples of these protocols are Analog, Digital and Internet Protocol which is referred to as voip. Analog is the type of protocol that Alexander Graham Bell invented with his first telephone. It is still a very common protocol in our daily lives. Then came digital protocol which allowed us to process more calls concurrently and thereby support larger phone systems for larger businesses. The clarity is generally better and the growth of communication continued. Computers enter our life and begin talking to each other with Internet Protocol so there is a standard for one computer to talk to another. The next item is to get the voice to go over the internet and then we have VOIP, voice over internet protocol.
Voice over Interne Protocol uses a term called packets to carry information from one location to the other. Since the term packet also refers to an easily identifiable item we use to package sugar, sweet n low, and whatever the blue packet of sweetener is called, I have used them by putting them end to end on a table to represent the flow of products moving along the internet. I can call the white sugar packets data because they are often times the most common of packets we see. Then there are the Blue packages which I can call voice since they are less common than the white data packets. Put them in a row and they become a train like sequence with different kinds of cars in the train carrying different products. Because of the many things that happen with the packets that we use to communicate, we have some safeguards with data that allow us to resend the packets if they do not arrive accurately. This is a very satisfactory solution in the data world, just resend and we will build the entire document when all the characters of the page arrive at the destination. Voice does not enjoy that same luxury. Just like in real life, if you didn’t hear everything someone said to you, the voice is gone. There are some techniques to help safeguard that from happening but it requires sophisticated equipment to control that on the internet. Most VOIP phones never leave the building and go out on the internet, they travel within the building to another telephone set, or the voice is converted to analog or digital and it proceeds outside the building using one of these protocols. For that reason, voice is only on the internet a small part of the time a VOIP telephone set is used.
If you have any further questions feel free to call Dennis Jenkins at 562-402-0100.