AH2700A to IBM PC Type Serial Port

To attach an Andeen-Hagerling 2700A bridge to an IBM PC Type Serial Port and command the bridge from the PC:

The official documentation will be in the "Operation and Maintenance Manual."  Here are some shortcuts.  You need a cable to physically connect, an unused serial port on the PC and a terminal emulation program running on the PC.

Physical Connection

• The connectors are of type DB-9 (9 pins) on the bridge and some ports of the PC.  Other serial ports on PCs have DB-25 (25 pins).  Bridge and PC serial ports are all male.  PC parallel ports are all female.  Do not cross connect serial and parallel ports: the result is usually permanent destruction of the parallel port.
• If you have a DB-9 male on the PC, the connection is usually simple.  A cable is needed with female DB-9 on both ends, and only pins 2, 3 and 5 are required.  But pins 2 and 3 must cross (that is, 2 on one connector attached to 3 on the other connector of the cable and vice versa).  This is usually called a null modem cable.
• If you have a DB-25 (male of course) on the PC, you need pin 7 on the DB-25 connected to pin 5 on the DB-9 (for ground), and pins 2 and 3 on the DB-25 connected to pins 2 and 3 of the DB-9 without reversing.
• Usually, there are several serial ports on a PC, and you need to know which you are using.  If you can't tell, try finding out which ports are already attached to other things, so narrowing down the number of possibilities.  In any case, you can always try them all.  Usually, the PC serial ports are named COM1:, COM2:, COM3: and COM4:.
• Attach the cable.  If your computer goes berserk, you've connected to a port with some driver running on it, and so disconnect the cable, reboot and see what you have done wrong.

Running the Terminal Emulation

• The standard terminal emulation program is called "HyperTerminal" and is on Windows 95, Windows 98, etc., though probably in different places in the Start Menu.  A reference to the program is probably under Programs|Accessories in Windows 95, and in Programs|Accessories|Communications in Windows 98.
• This selection may ask you immediately if you want a new connection (that is, the program is running) or merely drop you in a folder.  In this latter case, find "Hypertrm.exe" (or maybe just "Hypertrm") and select to run it.
• Now you are asked to name the connection, which is anything you please and can easily remember, or perhaps you must select from the menu File|New Connection first.
• You will then configure the connection through a dialog box, an entry of which will identify the device, usually, patronizingly, your modem.  You aren't interested in a modem, but the list should include entries of the form "Direct to COM<number>:" and select that, where <number> is the port on the PC to which the cable is attached.
• Press the button labelled "Configure" in this first dialog box to make another dialog box pop up that has the RS-232 configuration: including baud rate, data bits, parity, stop bits and flow control.
• Select these configuration parameters to match the bridge defaults (you can tweak them later): 9600 baud, 8 data bits, no parity, 1 stop bit and Xon/Xoff flow control.
• Press OK until the dialog boxes clear and you return to the main window of HyperTerminal.
• Press Enter several times as an experiment.  You should see a prompt from the bridge ">" (a greater than sign).  Then type "single" and press Enter to see that the bridge takes and reports a measurement to confirm that it is working.
• In case of trouble: try selecting from the HyperTerminal menu: Call|Disconnect and then press Enter again as an experiment.  (Sometimes configuration option changes don't get a clean restart without this command).  Also try toggling power on the bridge for the same reason.  Also try quitting HyperTerminal entirely and restarting that program.
• If the configuration seems bad, you can get back to the appropriate window in HyperTerminal by selecting from its menu File|Properties.
• If all goes well with HyperTerminal, select from the menu "File|Save" and the connection configuration will be available next time by the name you entered for the connection this time.
• There are many interesting problems that could occur that aren't described here.  Most of the problems are common to all RS-232 connections with PCs, so any generic documentation on the topic is useful.  And, although it takes a while to learn to use it, an RS-232 diagnostic tool with LEDs and jumper wires is very handy.  A useful hardware remedy is always to have a selection of RS-232 cables, adapters and doodads (variously called gender menders, sex changers and null modems) and attach these at random until something good happens.
• Eventually, while connected via RS-232 to the bridge, you will want to enter the command "define terminal video".