The ISDN connection is alive and working for me. There IS a difference
between 28,800 bps and 64,000 bps. ISDN stands for Integrated Services
Digital Network and provides digital communication transmissions end to
end instead of the digital to analog to digital transmissions we know from
our analog modem experiences. ISDN brings a magnitude of complexity that
is not present with analog communications. These complexities include the
service from the telephone company, the cost, the setup at the telephone
company, the setup of the "terminal adapter" (TA) in the computer, the
communications program setup, and the Internet Service Provider (ISP) setup
for the Internet connection.
ISDN service is offered at many levels of connection. The basic connection is called the Primary Rate Interface (PRI) and consists of two 56 Kbps or 64 Kbps B (bearer) channels and one 16 Kbps D (control) channel. This is the connection which I currently have. I am using one B channel (64 Kbps) for data and the other for voice/V.34 modem. This is due to the TA I am currently using.
Ordering ISDN service should be undertaken after a thorough review of the TA requirements has been made. In the case of the I-modem, I had to specify ISDN BRI service with two B channels, no packet switched data on each D channel, alternating Circuit-switched Voice and Circuit-switched Data (CSV-D) on the data B channel and Circuit-switched Voice (CSV) on the Analog Device B channel, automatic TEI assignment and RJ 45 wall jack. I had to specify my long-distance carrier. Next, I had to request the type of Central Office (CO) switch the I-modem would terminate into (Very important).
I also had to request the Service Profile identifier (SPID) per B channel, Directory Number per B channel, call types supported on each B channel, CO switch type and protocol, whether the bus configuration is multi point or point-to-point, and whether the switch automatically assigns Terminal Endpoint Identifiers (TEI).
SW Bell's San Antonio CO switch is currently the AT&T 5ESS using National ISDN-1 protocols with a multi point bus configuration.
Once I placed my order for ISDN service and had signed the contract and the SW Bell field representative had received his work order, he came by to survey the pole to house line in my telephone connection. The telephone company responsibility covers only that installation unless your have requested additional installation service like installation of the RJ45 outlet at the proper location IN THE HOUSE. ISDN comes into the house connection as a twisted pair cable. Each cable from the pole to the house contains two twisted pair phone cables. There are two pole cables into my house connection, giving me in theory, four telephones.
The house connection check found this to be true. And, one of the twisted pair contained the ISDN signal path. The line test at the box indicated this to be true. So far, so good.
After some discussion about additional service installation charges, we went into the house and into my office to test the connection at the wall plug. I had to call my SW Bell ISDN service representative to make sure that the extra charges were not assessed. (The installation service department does not talk to the ISDN department.) The test unit again indicated that I had ISDN signals at my wall unit. The call to the ISDN service desk had also straightened out the confusion about the RJ 45 wall jack required by my TA. Be sure to specify the type wall plug connection in the service order, as some TA units use RJ11 jacks and others use the RJ 45 jacks. This ended the SW Bell involvement in my installation process for a while. The field representative was at my house for less that 20 minutes total.
This is the U interface connection from the BRI line (twisted
pair) for the connection.
The I-modem contains many features not found in analog modems. It's primary feature concerns the TA ability to communicate at speeds up to 64 Kbps. This model contains both NT-1 and analog device jacks as well as internal power supply. The power supply is important as ISDN lines do not contain electrical connections to support dial tone. The analog device jack supports analog telephones, fax machines, or modems allowing them to communicate over the second B channel. This arrangement also insures that the I-modem connects to devices which are not ISDN capable at the other end.
It supports the V.110 (switched 56 Kbps data rates) and V.120 (64 Kbps data rates) protocols for digital connections as well as the V.34 protocols for analog connections. This is known as Universal Connect (UC) wherein the I-modem first tries a digital connection and switches to analog mode if the other end does not respond to the ISDN connection. It fully supports Adaptive Speed Leveling (ASL) and falls back to next lower speed if poor line conditions are detected. As soon as conditions improve, it switches to the higher levels.
Data integrity is supported under the V.42/MNP (error control)
and V.42bis/MNP5 (data compression) protocols. Typical file compression
is from 2:1 to 4:1.
Remember to record the settings. I mark the manual illustrations with a date to record how I setup the card. Install the card in the computer. One last physical setting must be made on a set of DIP switches on the I-modem bracket. I used the factory default which tell the I-modem to act on AT commands and load NVRAM settings at power-on or reset.
The next step is to configure the I-modem software. A software utility program named "Courier I-modem Configuration Manager" is included with the package. It is installed from Windows Program Manager in its own sub-directory. This establishes the utility as a Windows program. Opening this program brings the configuration screen up. This screen is divided into three areas with a row of Windows Open Bars at the bottom. The top section contains the fill in blanks for the DATA CHANNEL.
The middle section is for the ANALOG DEVICE CHANNEL. Within this section are blanks for Audio Port and Ringing Signal. The numerical selection is a range from 0 - 9 in both cases. The bottom section is for the COM PORT. There is a pull-down blank for switch protocol selection and bus configuration.
The first step is to establish the COM port and IRQ in this program.
This is done by clicking on the At this point set the SWITCH PROTOCOL TYPE and BUS CONFIGURATION
pull down windows. The switch type choices are AT&T 5ESS "Custom",
National ISDN-1, National ISDN-2, or Northen Telecom DMS-100. SW Bell San
Antonio uses National ISDN-1. The Bus Configuration choices are either
Point-to-point or multi point. I used multi point.
Next establish the ANALOG DEVICE CHANNEL entries which are similar
to the above settings. First, set the SPID number in the SERVICE PROFILE
ID. Second, enter the CALL TYPE with choices of either Speech; or Modem
/ Fax. Third, set the DIRECTORY NUMBER . Forth, set the TERMINAL ENDPOINT
IDENTIFIER. Fifth, set the AUDIO PORT and RINGING SIGNAL with numerical
choices of 0 - 9. Sixth, set the DIALING METHOD with choices of either
Standard Analog (overlapping) or Send All Digits at Once (en-bloc).
Save the configuration using the [Save] button at the bottom of
the screen. Then select the [Test] button to test the configuration. A
pop-up screen appears entitled "I-modem Switch Connectivity Test". Under
Status, there are two blanks which are filled in by the test. One IS titled
PHYSICAL INTERFACE, the other, DATA LINK LAYER. There is a Timeout blank
which counts down for the test. Both blanks must indicate :ACTIVE for the
test to be successful.
USR finally recommends that a communications program terminal
test be conducted to check out final connectivity. This can be done with
the Quicklink II or Windows Terminal programs.
It was at this point that I got extremely friendly with the USR
Technical Services staff. There was a physical problem with my I-modem
which required that it be mailed back to USR. USR opened a Service Order
which remained open for the duration of the problem, including being able
to e-mail the Tech Rep who first handled the problem and followed it through
the re-manufacturing process at USR. USR did a good job in this case.
One drawback of Chameleon as with other Windows communications
programs is that each uses the Windows 3.xx comm drivers as the program
drivers. This is the case with Chameleon. The comm drivers in Windows for
Workgroups is limited to 19,200 bps. This is a limitation. I have added
a third party comm driver set to my WFW computers. This program is by Pacific
CommWare and is named TurboCommander. This driver set allows me to
set my terminal speed at ISDN rates. I see 6400 characters per second (CPS)
receive which is 64,000 bps.
The cost of ISDN service is much greater than analog POTS service.
The telephone service contract is for two years and costs $61.74 plus tax
for a total of $68.03 per month. The initial contract for two years had
a minimum connection fee of 93.00 which is paid out over the first year.
The second year will be cheaper. The USR Courier I-modem also carries a
greater cost. It is normally priced at $700.00. It was obtained during
the Alamo PC special offer from US Robotics at $436.50. Other ISDN TA s
are less costly. And, many of them provide bonded B channels for 128 Kbps
speeds.
ISDN as it is being offered today is better suited for small business
or at home business where high data rate transfers are necessary. Those
instant graphics are really great, however.
John Woody is a telecommunications consultant specializing
in communications, networks, and Internet training. He is the Telecommunications
Special Internet Group Co-Chair.
Internet Communications
Upon return of the I-modem, I proceeded to finish the Netmanage Chameleon
NFS 4.6 program installation. The Chameleon and ISP procedures were straight
forward. I selected the normal setup features from the Chameleon "Custom"
screen and answered the fill-in or pull down items. The connection is established
with my ISP as a Point-to-Point (PPP) dial-in account. The modem setup
section identified the USR Courier I-modem as one of the pre-programed
selections.
Conclusion
The ISDN connection certainly makes surfing the Internet a breeze. Browser
downloads are rapid. File downloads are very fast. In many occasions, the
download has taken place before the system really gets up to speed. ISDN
and its related equipment are more complex than regular analog communications.