July 5, 2017

Mr. Watson, Come Here: A History of the Development of the Intercom (Part 2)

In the first part of this series, we discussed how the words "Internal Communication" led to the now common term, Intercom. We also talked about how the first intercom systems were known as voice tubes; tubes that carried voices acoustically. Although these were very crude systems compared to later electrical products, they did actually work. Some types of voice tubes are still in use today.

Like many other technologies, electrification changed intercom products radically. Before the electrical intercom could exist, one invention had to proceed it.

The telephone.

Bell making the first telephone call

When Alexander Graham Bell sat in one room in his Boston home, raised a transmitter tube to his mouth and then said, "Mr. Watson, come here. I want to see you", he was talking from that room down to his assistant in the basement, Thomas Watson. Watson, an engineer and employee of Bell's, once claimed that Bell had spilled battery acid on his leg and was genuinely calling for help. However, Watson later said that he could not be certain if this took place during the first test or in subsequent research. In any case, Bell documented the event in his journal on March 10th, 1876, making the first words spoken over what would later become the telephone, revolutionizing communications around the world.

One of the first systems ever patented was built by the Kellogg Switchboard and Supply Company in 1894. It's main purpose was for use in apartment buildings. Some early apartment buildings had a pull-wire, then later electrical, signaling system. A prospective visitor would pull a handle, or push a button on a panel, which would then signal the tenant that someone wanted inside. However, because they couldn't see or talk to who was signaling them, they ran the risk of letting in someone they didn't know, like a burglar.

As is true today, the more upscale apartment buildings in major cities had doormen to guard the building. Prior to the intercoms being available, these men would have to lock out the person asking for entry and go up to the tenant's apartment to ask if the tenant wanted to see the visitor or not. As apartment buildings became larger, this process became frustrating to both the tenants and the visitors.

Early Kellogg Phone

The Kellogg system added a telephone-type circuit to the signal panels. An earpiece and mouthpiece resembling the old-fashioned candlestick telephones allowed the tenant to talk to the visitor directly, instead of having the doorman run up and down to ask the tenant in person.

In the late 1930's, an engineer named Allan C. Bernstein started a company called Adams Laboratories that took the apartment intercom idea into the workplace. Ultimately, Adams Laboratories became the manufacturing arm of Executone Corporation, with Bernstein as President. The first product was a simple two-station system, called the "boss-to-secretary" system. This migrated into further point-to-point wired systems, including one of the first "patient-to-nurse" hospital communication systems ever used. Over his lifetime, Bernstein developed and held many patents until his death in 1987.

RMS Queen Mary's Loudaphone

One unique intercom system for use in noisy environments was made in England in the 1930's. Called the Loudaphone, it was installed in places with high background noise, such as trains or ship engine rooms. For example, the RMS Queen Mary had a Loudaphone system in use in the engine room areas.

After the Bell System monopoly was established in the early 1920's, the local telephone companies owned by Bell, then later American Telephone and Telegraph (AT&T), were the only convenient source of equipment and services for regular land-line telephone systems. This gave them a perfect opportunity to also be the provider of intercom systems.

Multiple desk phone intercoms

In old movies from the early part of the twentieth century, some of the scenes set in offices show a desk with two or three phones. Many times, one of the phone would be a part of an intercom system within the building. It wasn't until more sophisticated systems came along that the phones used for outside lines also had an intercom tied to them. However, not all businesses took advantage of this capability. Today, this is still the case.

As time passed, the needs of the marketplace caused manufacturers to make a lot of progress on new features. Speaker-based intercoms, such as those used in naval ships in WWII, became common in the commercial world. Since these operated like a speakerphone, they didn't require a handset. More than one person at a time could participate in the conversation. Noise-cancelling circuits for loud areas, public address capabilities, and other similar modern features made it easier for end users to find a system that suited their needs.

Wires, wires and more wires

One large cost factor in intercom installation was the wiring that had to be run inside the building. Pulling wire is extremely labor-intensive and it can be the most expensive part of an installation. To help with this, manufacturers came up with wireless systems that function like speakerphones, but use radio frequencies instead of wiring. Another unique solution that was developed became know as a Powerline system. A Powerline is when the intercom hardware uses the wiring that provides power to the outlets as a path for the signal.

In our next installment, we'll talk about the current state-of-the-art intercom technology and address two of the largest users of intercom products - the entertainment and broadcasting industries.

In case you missed Part 1 of this series:
    Part 1: Totally Tubular: A History of the Development of the Intercom

Paul Black is a freelance writer and broadcast engineer in Northern California. He holds a Certified Professional Broadcast Engineer certification from the Society of Broadcast Engineers and an FCC Lifetime General Class Operator License. He is a licensed amateur radio operator (call sign N6BBZ) and has worked for several broadcast companies, including Bonneville Broadcasting, RKO General Broadcasting, and CBS Television. Visit his website at www.paulblackcopy.com

June 27, 2017

Totally Tubular: A History of the Development of Intercom (Part 1)

People have always needed to communicate over long distances. From the smoke signal used by Native American tribes, to the telephone, to email via the Internet, the ability to communicate at a distance is a need that goes back through the millennia.

Equally so, communicating over smaller distances has also been important. Talking from one floor to another in a single building, or within any large area (such as inside a warehouse) requires some form of internal communication. 

From "internal communication", we get the now common term of "Intercom". This term is generally used as the name of a device or system that allows people to speak to each other from one room to another, or across a large open area inside a structure.

Before electrical systems were common, the usual way to get someone's attention was by some form of signaling. As an example, communicating in a large mansion-style home from the parlor to the servant's quarters was done by pull ropes that were connected to bells that would ring - when the rope was pulled, the bells would ring, grabbing the attention of the servant. When electrical signaling devices became more commonplace, these pull ropes were replaced with wired pushbuttons that would trigger a buzzer that would sound in the servant's quarters. Whether with the pull ropes or the wired pushbuttons, the servants were only alerted that their services were needed; therefore they needed to walk from one area of the house to the other to find out what was needed.

Being able to actually talk to a person in another part of a building would be more efficient. The result of this need of efficiency was the development of an acoustical communication system, or more simply, a voice tube. A voice tube is a hollow tube or pipe that was run from one place to another, allowing people to talk back and forth to each other from different ends of a building.

The idea for the original voice tube began back in the early nineteenth century by the French scientist, Jean-Baptiste Biot. His unusual choice of laboratory in which to test his theory - the water pipes of his home city of Paris. From his experiments, Biot discovered that smaller pipes carried sounds over amazingly long distances. Larger pipes just didn't work as well for carrying sound.

In 1849, Scientific American magazine published an article describing what they called as an acoustic telegraph - a tube made of gutta percha (a latex-like material that's produced from the sap of trees that grow in Malaysia). The article claimed that a tube made of this material and of the proper size could send voices for several miles.

Later voice tube developments included work done by Antonio Meucci, an Italian immigrant scientist who built an acoustic speaking tube system in his home in New York. He later was attributed for his work on what eventually became known as the telephone.

Early aircraft models were usually of the open-cockpit design and were extremely noisy. Instructors had to scream at their flying students in order to be heard above the sound of the engine and the slipstream noise. So, in 1917, at a flying school in Gosport, England, an instructor named Robert Raymond Smith-Barry sought to overcome this problem with some rubber tubes that had a funnel on one end, and a pair of primitive headphones made of cloth and rubber on the other end. The student wore the headphones and the instructor spoke into the funnel. Smith-Barry called his invention the Gosport Tube, after the town the school was in. This became a commonly used item for flight instruction until as late as the 1930's when closed cockpits and electrical intercoms became the standard in aircraft.

In 1926, the Bureau of Standards of the United States Department of Commerce issued a paper that could be purchased by the US Government Printing Office for a pricey 15 cents, entitled "Transmission of Sound Through Voice Tubes". It is an exhaustive study of the physics of sending sound via hollow tubes, including photographs and mechanical drawings of the tubes used in the test procedures. The US Navy actually initiated the request to the Bureau of Standards for these tests to be done. The Navy is one of the prime users of acoustic voice tube technology, and that is true even to this day. Currently, modern Navy landing craft (or LCU's) use voice tubes to communicate from their upper deck to control centers below deck. Other naval vessels also use them, as well as merchant marine cargo ships.

The major advantage of a voice tube system over an electrical communication system is its simplicity and reliability. Voice tubes are impervious to the problems plaguing electronic systems, such as power failures, broken or shorted wiring, and invasion by moisture. So, despite the sophistication of modern electrical intercoms, acoustic speaking or voice tubes remain in use. Because of this, voice tubes make these a good choice for these applications.

In our next installment, we'll look at the rise of the electrical intercom systems, how they developed from the days of the invention of the telephone, and why some of the first applications of these products were for safety and security purposes.

Paul Black is a freelance writer and broadcast engineer in Northern California. He holds a Certified Professional Broadcast Engineer certification from the Society of Broadcast Engineers and an FCC Lifetime General Class Operator License. He is a licensed amateur radio operator (call sign N6BBZ) and has worked for several broadcast companies, including Bonneville Broadcasting, RKO General Broadcasting, and CBS Television. Visit his website at www.paulblackcopy.com

June 20, 2017

Do You Need a LAN or a WAN?

When designing an IT network topology, you might want to consider a Campus Area Network (CAN), a Metropolitan Area Network (MAN) or a Tiny Area Network (TAN), but most certainly a Local Area Network (LAN) or Wide Area Network (WAN) will do the job. All of these networking schemes utilize the same switches and file transfer technologies and are used to connect computers and devices, allowing them to communicate in a specific geographical area or region.

You might be most familiar with the computer networking terms like LAN or WAN, which are thrown around a lot in conversations about setting up IT networks and collaborative environments, but what do they really mean to your organization? 


A Local Area Network (LAN) is a group of computers and network devices that are connected together, usually within the same building. Examples could be a small office or production facility, a single building or multiple buildings located on campus. 


A Wide Area Network (WAN), as its name implies, connects several LANs together (whether nearby or in different parts of the world) and is typically used by an enterprise-level installation (a corporation or organization) or local governments that make civic information easily accessible to the public.


The technology employed - routers, servers, cabling, desktop clients for users - is high speed and relatively expensive. LANs tend to use high-speed connectivity technologies like Ethernet (CAT5/6 cabling) or Token Ring (all computers are connected in a ring or star topology). WANs most often use technologies like MPLS, ATM, Frame Relay and X.25 for connectivity over long distances.

LANs use Layer 1 devices, like hubs and repeaters, and Layer 2 devices, like network switches and bridges. WANs use Layer 3 devices, such as routers, multi-layer switches and specific devices like ATM or Frame Relay switches.

One LAN can be connected to other LANs over any distance via telephone lines and radio waves, while computers or other networked devices connected to a WAN are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites.

The major advantage of a LAN is the speed it can reach. With a LAN, it isn't uncommon to see technology that supports 1Gbps file transfers. Most agree that a LAN can operate up to 30x faster than a WAN. The further the distance, the slower the network. However, the major disadvantage with a LAN is that it is only good as far as you can reach an Ethernet cable or WiFi signal. Simply put, you cannot buy an Ethernet cable that will reach throughout an entire building, and a WiFi connection rapidly deteriorates as you get further than a few dozen miles away.

A WAN connection is generally harder to setup, but there are many creative ways to do so. One very common way is renting a line from an Internet service provider and using their network (that's already connected to the entire world) and connecting Point A to Point B. Another way to do a WAN is connecting the devices with various wireless technologies, like cellphone towers or satellites. As you can imagine, all of these are much harder to create than setting up a LAN, and almost always demands high level professional setup and maintenance.


LANs are generally more secure than WANs, but, of course, WANs enable more widespread connectivity. And, while LANs tend to be owned, controlled and managed in-house by the organization where they are deployed, WANs typically require two or more of their constituent LANs to be connected over the public Internet or via a private connection established by a third-party telecommunications provider. As for actual reliability, LANs tend to have fewer problems because there are less systems to deal with. A WAN tends to be less fault tolerant as they consist of a large number of disparately located systems that have to be reliably connected.


One of the big disadvantages to implementing a WAN is the cost. Having a private WAN can be expensive because of the technology required to connect two remote places together. However, WANs using public networks can be setup very cost-effectively using Virtual Private Network (VPN) hardware and software, which allows a desktop computer to transparently connect to a remote network as if you were physically attached to that network. For security, the communication link between your computer and the remote VPN hardware is encrypted while using the VPN.

The maintenance costs are often lower with a LAN because it covers a relatively small geographical area, while maintaining a WAN is difficult because of its wider geographical area.

In the end, it's clear that those implementing a network - whether a LAN or a WAN - should take a hard look at how they plan to use that network and who will use it. Each topology has its advantages and disadvantages that can affect an organization's productivity significantly. Which one you choose ultimately depends on costs and your business model.