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Setting Up a Remote TerminalA step-by-step tutorial |
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From "Migration", Access to Wang, November 1995 |
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The last few months I have received much interest in the details of setting up a remote terminal for a Wang system, using a Wang 2110 terminal or a PC emulating a 2110 terminal. In response, here is a step-by-step description of the process - from the VS controller to the end user.
Setting up a remote terminal using Wang's 2110 protocol involves the following steps:
1. Set up VS controller: Install and configure an appropriate VS controller (IOC).
2. Set up telephone connections: Provide telephone connections at the sending and receiving locations. These should be normal voice-grade lines without special services such as Call Waiting.
3. Set up modems: Install and configure modems at the sending and receiving ends.
4. Set up workstation: Install terminal (2110 terminal or PC).
5. Test and train: Test terminal use under actual conditions. Train users in differences with remote connections, including keyboard differences and file transfer and remote printing.
2110 terminal connections require specific asynchronous communications connections with the VS through an appropriate controller, such as the 23V86 Multi-Line Telecommunications (MLTC) controller. Other controllers that support 2110 connections include the Asynchronous Device Controller (ADC) and Extended Asynchronous Device Controller (EADC) series.
Controller ports can be configured for a variety of parameters, including the speed of the connection (baud rate), the size of the work (bit size) and parity (odd, even, none). For the sake of simplicity, here are my recommendations for the values of these settings:
Item Value Baud rate 9,600 Parity None Stop bit 1 Data bit 8 These settings provide adequate service and fit well with conventions used in other dial-up service settings, such as on- line services. The baud rate selection must be matched to the capabilities of the modem: 2,400 baud is the minimum speed for practical purposes, while the maximum speed supported (19,200 baud) is not available from most modems. One of the speed selection options is AUTO, which, in theory, should adjust the speed of the connection to that of the incoming modem; in my experience, this setting does not work correctly and should be avoided.
The choice of modem speed should also be based on the capabilities of the remote workstations. Since the 2110 connection is fixed-speed, the end user must be able to connect at the same speed. With the cost of fast external modems hovering around $150 retail, 9,600 is the most typical choice here.
Finally, you will need an appropriate cable to connect the modem to the VS controller. Wang supplies cables with the IOC that work in most circumstances. The Wang cables - which are usually identified by a picture of a telephone molded into the ends - use 25-pin male connectors (DB25M) on both ends and have all 25 wires connected straight through. Cables purchased through other sources may have as few as four of the 25 wires connected and often will not work. Ask for a "straight-through" cable if you must purchase cables.
Telephone connections for modems are not as difficult to get set up as in the past, mostly due to better acceptance and understanding by the phone companies. Virtually any standard voice-grade telephone line can be used, including those routed through local PBX (Private Branch Exchange) systems, such as those found in most large organizations. If you are setting up new lines, ask for a "flat business line" - telephone jargon for a line with its own telephone number and wall jack. Do not use phone features such as Call Waiting on a line use for data communications as they will disrupt the data connection.
One important consideration in selecting inbound telephone connections is access to the connection by your users. If you order a new telephone line for each new connection - the simplest method of establishing new connections - you will spend more per connection than if you establish a single telephone number and a "pool" of shared modems. On the other hand, a single receiving modem for each user ensures that your users never hear a busy signal. I recommend you consider the requirements and expectations of your users when deciding how to set up your lines.
Nearly any modern modem can be used for 2110 connections, including a number of inexpensive models that can be purchased in most computer stores. The primary difference between expensive "commercial-grade" modems and less expensive models is an intangible quality of ruggedness: the ability to answer and connect reliably, even when line quality and other conditions are not ideal. Modem technology has steadily improved, and the difference is less noticeable today.
Several years ago it was common for modems to use switch settings and other physical means of setting modem options. Most modems are now "software-controlled"; that is, you program the modem through commands entered by a terminal or PC. Modems at the VS end of the connection will require special setup, so you will need a terminal or PC to use these units.
One of the trickiest aspects of establishing dial-in connections is setting up the modems on the host side, and the VS is one of the pickiest hosts in this regard. In general, you must set up the modem so it uses hardware flow control (the flow of information is controlled by the modem and VS controller), operates silently (the results of commands are not displayed), and answers the telephone when it rings. Specific setup for the VS, unfortunately, varies widely according to the default settings (the factory setup) and extra features of the modem.
Almost all modems use the AT command set - originally developed by Hayes - to set their options. Some of the AT commands are standard, but modem manufacturers have added extended commands to control new modem features - such as Caller ID, fax/data/voice detection, and the like. Most of the extended commands have an ampersand (&) as their first character.
The AT command set gets its name from the AT prefix used for all modem commands, which is short for "attention." To demonstrate these commands, connect a terminal (or a PC emulating a terminal) to the modem, enter AT and press return. If you are properly connected, the modem should reply with "OK". Next try AT &V (or AT I4 for US Robotics products) to view the current settings of the modem; the result should be a cryptic listing showing the active profile (current setup in use) and one or more stored profiles (groups of settings that can be recalled with a single command).
Entering a command to change a value in the configuration will affect only the active profile, and the change will remain in place until the modem is turned off or reset (command AT Z). To save commands in non-volatile (permanent) memory, you must write them back to a memory location. The typical command for this is AT &W, which will write the values of the active profile into a stored profile. When the modem is cycled (reset or powered off), the values in the first stored profile are loaded into place.
When I configure a new modem, I always begin from a common point and add commands to establish my new settings. The process works as follows:
Description Command Set to factory defaults AT &F (Enter commands to modify settings as needed) Review new settings AT &V or AT I4 Save new settings AT &W Here are some specific setups for popular modems:
Name Command Line US Robotics AT S0=1 &A1 &I0 &K1 &M4 &N0 &S0 NEC AT S0=1 \Q1 &S1 Q1 E0 &C1 These should be viewed as a guide and tested using local terminals and modems. Be sure and write the results to a stored profile before turning the modem off.
Setting up the terminal side of a Wang connection requires a terminal (or PC and terminal emulation software), a modem and cable, and a telephone line. Most of same considerations apply to the phone line, but most modems should work well as they come from the box (e.g. using factory defaults). PC emulation software is available for computers running MS-DOS, Windows, and for the Macintosh. Emulation software has many advantages over a Wang 2110 terminal, including the ability to transfer files to and from the remote PC (provided you have the related VS software from the same manufacturer).
If you use a PC as a remote workstation, carefully consider the type of keyboard you will use. Since only Wang PC keyboards have 16 function keys and other Wang-specific keys, emulation software must provide access by mapping these keystrokes to other keys. For example, PF16 could be SHIFT+F6 or ALT+F6. Most users get used to these differences quickly, but switching between keyboard layouts can get confusing.
If you already use a terminal emulation package and would like to save some money, it is possible to use a VT-100 terminal (or equivalent) with a Wang 2110 controller. Disadvantages to this approach include speed (the 2110 protocol is faster), support for PF keys, and file transfers. This approach can work well when you already have dial-in connections to Unix or other hosts using standard terminal packages. Again, consider the options for the keyboard layout carefully and choose a package that allows you to change the key arrangement.
The information for this discussion was drawn from actual experiences in setting up 2110 connections. As always, some items were covered in less depth due to space limitations. If you are interested in additional information, please contact me through the magazine.
Figure 1: Sources of Wang 2110 emulation software
Software Business Applications (division of Sentinal Technologies)
708-769-4300
2110 emulation and file transfer for PC compatibles running MS-DOS.DPZ Systems
2110 emulation and file transfer for PC compatibles running MS-DOS and Apple Macintosh.MacSoft Software
2110 emulation and file transfer for PC compatibles running MS-DOS.M/H Group
2110 emulation and file transfer for PC compatibles running MS-DOS and Apple Macintosh.
Copyright © 1995 Dennis S. Barnes
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if the source of the information is clearly identified