This section provides further information about Windows 98 communications tools.
The Windows Telephony API (TAPI) is an important part of the Windows Open System Architecture (WOSA). TAPI lets developers of virtually any skill level create powerful, easy-to-use, and effective telephony applications. TAPI provides full client/server telephony, and is open, comprehensive, scalable, and integrated.
Open
TAPI was defined with substantial, ongoing input from the telephony and computing industries from all over the world, so it is truly an open industry standard. TAPI-compatible applications can be run on a wide variety of personal computer and telephony hardware and can support a variety of network services.
Comprehensive
TAPI supports many telephony features. A developer can program telephone capabilities into most general-purpose applications. TAPI supports Unicode, so it is easier to make applications work globally. In addition, it integrates call control and other WOSA elements. With Active Controls for telephony provided by a variety of vendors, corporate developers can put together powerful telephony applications.
Scalable
With TAPI, you can have CTI applications that are affordable for one person or can scale to support thousands, because TAPI supports the widest array of call models. With TAPI you can run several telephony applications simultaneously on a client or server computer, unlike with other competitive APIs.
Integrated
TAPI is tightly integrated with Windows 98.
There are several ways to add telephony drivers from other vendors, if necessary. Some telephony drivers work over the network and consist of software only. If this is the case, the software can be installed through the Add/Remove Programs option in Control Panel.
Hardware drivers can be installed through the Add New Hardware option in Control Panel, unless the hardware requires its own class installer. In this case, the hardware should come with a standard Setup program to install it.
Integrated Services Digital Network (ISDN) is the digital telephone service that works over existing copper telephone wiring. There are several types of ISDN service, but the most appropriate type for individual computer users—and the type that this section focuses on—is the ISDN Basic Rate Interface (BRI).
Basic Rate ISDN divides the telephone line into 3 digital channels: 2 B channels and one D channel, all of which can be used simultaneously. The B channels are used to transmit data, at rates of 64 Kbps or 56 Kbps (depending on your telephone company). The D channel does the administrative work, such as setting up and terminating the call and communicating with the telephone network. With two B channels, you can make two calls simultaneously.
Most of the world’s existing telephone network is already digital. The only section that typically is not digital runs from the local exchange to your house or office. ISDN makes that final leg of the network digital.
Unlike analog telephone service, ISDN service is not yet available everywhere. Your telephone company must have installed the necessary equipment in the central office that serves you.
Provisioning is a telephone company term for the configuration of your line on the telephone company’s end. A normal analog telephone line comes with a few options, such as Call Waiting or Caller ID, but it is not necessary to choose any of them. An ISDN line, on the other hand, has many, many options, and choices for all of them must be defined in order for the line to function.
In addition to the configuration the telephone company must do at their end of your ISDN line, there is also some configuration you must do at your end. You need to know three pieces of information supplied by the telephone company to make your ISDN service work with Windows 98:
Most ISDN hardware adapters need to know what type of switch they are connected to. The switch type simply refers to the brand of equipment and software revision level that the telephone company uses to provide you with ISDN service. There are only a few types of switches in the world and usually just one in countries other than the United States.
The second type of information is your phone number or numbers. In some cases, each B channel on an ISDN line has its own number, while in other cases both B channels share a single phone number. Your telephone company will tell you how many numbers your ISDN line will have. Separate numbers may be useful if you plan to take incoming calls on your ISDN line.
The last type of information is the Service Profile Identifier (SPID), which is only used in the United States and Canada. The SPID usually consists of the phone number with some additional digits added to the beginning and end. The SPID helps the switch understand what kind of equipment is attached to the line, and if there are multiple devices attached, helps route calls to the appropriate device on the line.
There are two types of ISDN hardware adapters: internal and external. Internal ISDN adapters are cards that you put inside your computer. External adapters connect though a port on the back of your computer.
These ports impose certain limitations. Most personal computer serial ports will not transmit information faster than 115 Kbps, which is less than ISDN’s maximum data speed of 128 Kbps. These serial ports impose overhead on the transfer of information between the computer and the external adapter, further slowing data speeds. An external ISDN modem can impact the performance of your system, because an external adapter places heavy requirements on the CPU. To use an external ISDN adapter, it is recommended you have a 486/66 MHz or faster processor.
There are also potential interoperability issues with external adapters, because higher level protocols like PPP or authentication are implemented in the modem itself. These protocols are evolving quickly and can be difficult to update in the modem should you want to install new protocols or fix bugs.
Once you have ISDN service, you need to know which ISDN interface your equipment expects. There are two ISDN interfaces. The U-Interface carries ISDN signals over a single pair of wires between your location and the central office. This interface is designed to carry ISDN signals over long distances. The Subscriber/Termination (S/T) Interface uses two pairs of wires to deliver the signal from the wall jack to your ISDN adapter or other ISDN equipment.
Some ISDN adapters sold in North America connect directly to a U-Interface. If the computer is the only equipment to be connected to an ISDN line, this type of adapter is the easiest to install.
ISDN service from the phone company officially ends at what is called the demarcation point ("demarc"), usually just inside the building. You are responsible for the "inside wiring" from the demarc to your ISDN equipment, including the wall jacks. Direct wiring between the ISDN wall jack and the demarc (also known as a "home run") is recommended. The telephone company or an electrical contractor will install and maintain the inside wiring for an additional charge.
If you are just connecting your personal computer to the ISDN line, the wiring requirements may be very simple. Many homes and offices are wired with extra sets of telephone wires, and one of those sets can be used for your ISDN line. There are a number of possible wiring pitfalls, however:
For more information on wiring issues, consult your telephone company or an electrical contractor.
The NT-1 (Network Termination 1) is a device that is required to connect ISDN terminal equipment to an ISDN line. The NT-1 connects to the two-wire line that your telephone company has assigned for your ISDN service. Your ISDN service will not work if the NT-1 plug is not connected to a working electrical outlet.
Two types of jacks are associated with ISDN:
It is possible to connect up to eight devices to a single ISDN line. These devices can include network routers and bridges, Group 4 ISDN fax machines, and ISDN telephones, as well as traditional analog telephone devices. ISDN is intelligent enough to arbitrate the use of the two B channels between these devices (up to two devices can be in use simultaneously) and route incoming calls to the appropriate device.
Instead of connecting the ISDN line to a single computer, it is possible to connect an ISDN line to a LAN so that all the computers on the LAN can share the ISDN line. This requires an ISDN network bridge or router.
It is also possible to connect several ISDN devices to a single ISDN line. For example, you might wish to have an ISDN adapter in your computer, an ISDN telephone for voice calls, and a Group 4 ISDN fax machine, all connected to the same ISDN line. Incoming data calls would go to the personal computer, voice calls to the telephone, and fax calls to the fax machine. To support this configuration, you need an NT-1 that supports multiple S/T Interface connections. Each device must be connected to the NT-1. Each device also needs its own SPID to ensure that the telephone company can route calls to the appropriate device.
In addition to ISDN devices, some NT-1s or ISDN adapters also support analog telephone devices, such as telephones, data modems, Group 3 fax machines, and answering machines. The NT-1 or the ISDN adapter converts the analog signal into ISDN and vice versa.
Because ISDN is a digital service, it is sensitive to outside interference, and certain factors affect the quality of ISDN connections to the telephone network and the Internet. The computer connecting to the ISDN line must be within a given distance of the telephone company’s central office equipment that serves the computer for the ISDN connection to work. The maximum distance allowed between the computer and the central telephone office is typically 18,000 feet. Additionally, ISDN connections can be adversely affected by telephone lines that are not wired using twisted-pair wiring.
The most appropriate type of service for small Internet Information Server sites is ISDN-Basic Rate Interface (ISDN-BRI). The most appropriate type of service for medium to large Internet Information Server sites is ISDN-Primary Rate Interface (ISDN-PRI).
ISDN - Basic Rate Interface
ISDN-BRI divides the telephone line into three digital channels: two bearer channels, commonly referred to as B channels, and one D channel. All three channels can be used simultaneously. The B channels can be used to send voice, circuit-switched data, or packet-switched data at rates of 56 Kbps to 64 Kbps. The maximum available transfer rate is determined by your local telephone company. The B channels function independently of one another. They can be used simultaneously for separate calls or combined to provide a total bandwidth of 128 Kbps. The D channel can transfer data at 16 Kbps and is used for signaling and control information sent between the computer and the telephone office. D channel signaling provides such functions as call setup, call monitoring, call termination, and enhanced telephony features.
When using ISDN-BRI, it is possible to perform several types of connections. For example, it is possible to have a voice conversation on one B channel, a circuit-switched data call on the second B channel, and a packet-switched data call on the D channel. The D channel can simultaneously complete all necessary signaling and call control functions.
ISDN - Primary Rate Interface
The U.S. standard for ISDN-PRI consists of 24 digital channels: 23 B channels and 1 D channel, commonly referred to as a 23 B+D connection. ISDN-PRI provides a total bandwidth of 1.544 megabits per second (Mbps) and is designed for transmission over a North American - standard T1 line connection.
The European standard for ISDN-PRI provides a total of 31 or 32 digital channels. Each of these channels is a 64 Kbps B channel, except for one that is the D channel for the entire group. In Europe, ISDN-PRI is designed for transmission over a European-standard E1 line connection. A PRI D channel can be used to control one or multiple T1 or E1 lines.
ISDN is a powerful but complex service and is not yet available throughout the United States. For this reason, getting ISDN can sometimes be confusing or frustrating. Microsoft provides an online service that can guide you through the ordering process. This service and useful information is available for computers running Windows-based operating systems. This service can simplify and streamline the process of getting ISDN for your Windows-based computer by helping you:
To use this online service, connect to the Microsoft World Wide Web site at http://www.microsoft.com/windows/getisdn/.
Note
Even if the right equipment is installed in your area, ISDN may not be available. To determine whether your particular wiring supports ISDN, your telephone company must perform what is known as a line qualification.
Support for ISDN is a built-in feature of Windows 98. ISDN requires Transmission Control Protocol/Internet Protocol (TCP/IP) and Point-to-Point Protocol (PPP), which Windows 98 fully supports. PPP is an industry standard that enables Windows 98 – based computers to support remote access networking in multi-vendor networks.