Michael Hermann graciously allowed CECI to reproduce his personal telecommunications primer written in the late 1990s. While it does not cover some of the more modern systems or Voice over IP, some of us still have those old copper based telecommunications systems in our homes back when VoIPP meant "voice over ivory princess phone."
If anyone knows where to find Mike, please let us know.
As we head into the 21st century, extraordinary advances in technology are propelling us into a telecommunications era in which there will be virtually no limit to the amount or type of information that can be transmitted from one point to another, anywhere in the world. Current advances promise an unparalleled wave of existing and new services in both residential and business markets.
In today's competitive marketplace, businesses rely on the effectiveness of voice and data communications to enhance productivity and efficiency in the workplace. As a company expands, its communications needs expand with it. "Downsized" companies sometimes experience growth in voice and data traffic when the workload is redistributed. How a company meets those needs will have an impact on its future growth and profit. Knowledge of the many available telecommunications services and applications can be essential to a company's success.
Only a few years ago, a call to a local telephone company would generate all the help available. Telephone company experts would determine the service that best met a company's specific applications needs, order all the necessary equipment, arrange for the installation, and train the company's personnel how to use it. Now that the choices are greater, the task of choosing the right service and the accompanying coordination responsibilities have shifted from telephone companies to the customer. A lack of understanding; however, can produce a high-tech nightmare. This article describes the most popular voice and data telecommunications services and the applications best suited to these services.
POTS or Plain Old Telephone Service is the most basic form of phone service; it's the mainstay of residential communications and still has widespread business use. Some businesses start with one line and never require anything more. However, growing businesses should plan the expansion of their telecommunications systems in order to stay ahead of customer demand.
Businesses can choose from a variety of telephone sets costing from as little as twenty dollars to several hundred dollars. The more expensive sets offer the features of a hold key, speed calling, last number redial, etc. and some can handle as many as four separate phone lines. Should a need more features, a phone company can add:
An answering machine can be added to take messages when employees are unable to do so. Most modern answering devices will let you call in from another phone to retrieve messages. Some answering machines have multiple announcements and mail boxes. Answering machines are available in cassette, microcassette and digital formats.
Voice Mail from either the local phone company or a private supplier adds an important additional capability, because it answers calls while you are talking on your phone instead of giving your customer a busy signal. Voice Mail can be a crucial addition to a company's telephone service because busy signals encourage your customers to call your competition. Small companies may wish to use both systems to maximize the usage of each line. Company personnel should periodically check their answering machines and voice mail systems and respond to customers' needs promptly.
Communications equipment needs and administrative equipment needs will grow as a business grows. A fax machine and a modem can turn a personal computer into a more powerful communications tool for small businesses. Although an intelligent switch can monitor the distribution of voice, fax and data calls, a regular telephone line allows the use of only one device at a time. If a phone, fax and modem share a single line, direct customer communications is cut off while receiving or transmitting a fax or data. As business expands, consider either extra phone lines, voice mail or a multiple-use service like ISDN (see ISDN and ISDN PRIMARY RATE INTERFACE, below).
As employees are added, communications needs continue to grow and manual multi-line phones will quickly become impractical. A key telephone system can increase a staff's productivity while helping to control network expenses by allowing employees to share a smaller number of telephone lines with a larger number of stations (phones). The ratio of line to stations is determined by phone usage.
Key systems can accommodate from 2 to 100 telephone lines and from 4 to 150 stations (telephones). They provide many useful features and may be either analog or digital. Analog systems are used almost exclusively for voice but digital systems may provide extra interfaces for the connection of fax machines or computers. Some provide Local Area Network (LAN) wiring, allowing computers to share data.
The main drawbacks of key systems are limited growth and incompatibility of different manufacturers' equipment. This is especially true of digital systems. Only phones designed specifically for your key system will work properly. Each system has been designed to strict size limitations; once a system reaches its limit, a company will need to purchase something larger.
PBX's or Public Branch Exchanges are highly intelligent transmission and information processing systems. Typically, a PBX can handle from one hundred to several thousand lines. In addition, they offer more sophisticated features than key systems. Electronic voice messaging, multiple attendant positions at various sites, least cost routing for long distance calls, energy management, and integrated voice and data are a few of the features available. Many now incorporate some form of "personal communicator" or wireless phone.
Automated Attendant systems answer incoming calls without requiring a receptionist's intervention. Callers are offered a menu from which they can select a department, directly dial the extension of the person they need to talk to, or dial 0 for the operator. A properly set up system can be a useful and efficient way to route calls. An improperly set up system tends to irritate customers. Thus, efficient planning is a necessity for these systems.
If a company receives a large volume of calls in a variety of departments such as customer service, catalog orders, or airline ticket reservations, an Automatic Call Distributor (ACD) is the most powerful tool for handling these calls. An ACD keeps track of incoming calls, assuring they will be answered in order by the next available operator. It's second major function is to provide information about call volume to aid employee scheduling for proper call coverage. The information provided can help a business determine how many people to hire and how many to have answering phones at any one time.
Centrex is a business telephone service provided by the local telephone companies. Instead of a key or PBX system, the switch in the phone company central office provides as many as 75 advanced calling features. Unlike key systems and PBX's that require expensive electronic controllers and switches, Centrex only requires phones, which helps to keep system start-up costs down.
Centrex has many advantages. Telephone companies continually update their switches adding the latest functionality to assure that Centrex will not become obsolete. Centrex systems have unlimited capacity and can grow or decrease as business dictates. Network maintenance is provided by the phone company at no charge.
Integrated System Digital Network or ISDN is the first service to deliver full digital connectivity that is both affordable and available to any size business or home. ISDN's Basic Rate Interface (BRI) offers three channels and up to eight devices can all operate on the same line simultaneously.
ISDN's voice service provides enhanced electronic key features which include multiple call appearances allowing a customer to handle multiple calls on the same line. Caller Identification displays the telephone number, and in some areas the caller's name, before you answer the call. This allows you to decide which calls to answer, leave for voice mail, or transfer to someone else. Conference bridging enables you to conference up to 30 people on the same call without loosing clarity or volume.
ISDN's high speed data capacity transmits information several times faster than the fastest modem. It provides a common digital network for world wide communications. It's end to end digital connectivity ensures high quality error free transmission. Simultaneous video, graphics, text, and audio applications will provide users with access to a broad selection of new services.
Because ISDN incorporates the features of circuit switched voice, circuit switched data, and packet switched data, its applications capabilities are numerous. It can be used to deliver enhanced voice services previously associated only with large key systems or PBX's. It can be used to provide high speed file transfer, Group 4 (high speed) Fax, high speed access to on-line data bases (this will become essential as information services become more graphics oriented), electronic mail, corporate work-at -home or telecommuting, remote LAN connections, distance learning, transaction services such as credit card verification and remote meter reading, video and PC teleconferencing, and disaster recovery.
Primary Rate Interface or PRI combines 23 ISDN "B" channels and 1 "D" channel onto a single pipe. These channels can be used either singly or in combination to provide voice, data, or video applications. PRI can be very cost effective for companies with digital PBX's or that have provided their work-at-home employees with ISDN to their homes. It provides the user the maximum flexibility in facility usage.
Primary Rate applications include consolidation of network facilities, video teleconferencing, LAN interconnection, disaster recovery, medical imaging, and many more.
Customers that transmit data continuously (e.g., more that eight hours per day), will probably find that using private line data services is more economical than using most switched services. Running at various speeds such as 64 Kbps or DS-0 (64,000 bits per second), 1,544 Mbps or DS-1(1,544,000 bits per second), and 45 Mbps or DS-3(44,736,000 bits per second) these channels can be used to transmit voice or data information. They provide nearly error free performance and a high level of security.
Applications include secure voice and data transmission, host to host computer connections, LAN interconnections, videoconferencing, electronic publishing, CAD/CAM ( computer aided design/computer aided manufacturing), and medical imaging.
Packet switching is a technique in which user information is divided into addressed segments called packets, which are sent through a shared network. Like packages trucked from one location to another, the packets travel available routes through the network and upon reaching their destination, they are reassembled to their original format. Customers are billed for the number of packets sent rather than the time spent on the network.
Packet Switching offers a cost efficient, secure, and reliable alternative to private line services. Applications best suited to this service include transaction services like credit card verification, security and fire alarm monitoring, remote meter reading, E mail, and access to on-line information services. Public packet switched networks like the Internet are less secure because of the number of sophisticated users and the global availability of the Internet.
Frame Relay (sometimes called fast packet) provides high speed packet data transfer at rate from 56 Kbps to 1.544 Mbps. Frame relay sets up a permanent virtual circuit between two or more customer locations. These circuits resemble private lines but in reality are shared by many other customers. Connections to multiple locations can be established over a single access line allowing the customer to consolidate traffic from many private lines onto a single frame relay line.
Frame relay is most effective in reducing large private line networks dispersed over a wide area, transmitting data between branch and central offices, CAD/CAM, LAN to LAN connections, and companies with rapidly expanding networks. A customer still pays for a Permanent Virtual Circuit (PVC) between two points (similar to purchasing a dedicated line), but instead of purchasing a physical line, the service provider
Frame relay has recently experienced explosive growth because it is less expensive to maintain than a private network. However, its new found popularity has providers struggling to keep up with demand and provide global connectivity. Permanent Virtual Circuits (PVCs) are readily available, but switched circuits remain promising, but elusive.
Some service providers (e.g., Ameritech, MCI, Sprint, MFS Datanet, LCI International, etc.) allow their clients to take risks in purchasing permanent virtual circuits with no guaranteed traffic. This allows a client to purchase the power and speed of frame relay for data transfers that are not time sensitive. The client takes the risk that the bandwidth necessary to complete a transaction will become available in exchange for a substantial cost savings.
Frame relay systems are popular with service providers because the frame relay supports SONET standards for fiber optic transmission. Service providers are also not reluctant to build large frame relay systems because the frame relay standards are compatible with faster, future switching technologies such as ATM.
ATM or Asynchronous Transfer Mode (not to be confused with Automated Teller Machines) is another high speed (broadband) packet switched technology allowing access at rates of 1.544 Mbps to 622 Mbps and possibly even higher. ATM uses cell-switching to provide previously unattainable high data speeds. One of ATM's key attributes is it's ability to transmit high quality voice and video. It will be used as a backbone to carry DS-1, DS-3, OC-3 (155 Mbps), OC-12 (622 Mbps), higher OC speeds, Frame Relay, and Switched Multimegabit Data Service (SMDS).
Primary applications include computer disaster recovery, super-computer access, medical imaging, high quality voice and video, and high speed LAN connections.
Wireless communications is on the verge of tremendous expansion. To date, due to technical constraints, cellular communications has been limited largely to voice. These barriers are beginning to erode, and mobile data access is becoming a reality. It is now possible to access data bases and exchange information from a mobile terminal miles away from the nearest telephone line. This trend will continue as wireless voice, data, and fax are combined, making the "mobile office" from remote sites anywhere on the globe a reality.
Integrating the services described in this section into a system that best suits your needs can be a very time consuming and frustrating process. Your goal should be to obtain the most effective and efficient service for the least amount of money. Applications that work well on one service also work well on other services, but erroneous choices can be costly. If you do not have a well-trained telecommunications staff, a qualified consultant can help you identify the critical issues and choose the service solution best suited to your needs.