COURIER HIGH SPEED MODEMS
The Synchronous Adapter Card
You will probably have to purchase and install a synchronous adapter card. These cards are multifunction boards that provide the following functions:
•A synchronous port from the DTE to the modem
•One or more synchronous protocols. Be sure to find out which protocol the Host mainframe requires before you purchase an adapter.
•Additional software functions. For example, you need to identify the type of computer or terminal you are using to the mainframe software. You will most likely also have to specify your application⎯that is, identify the mainframe resources you want to use.
Setting the Modem
When the modem is set to Online Synchronous mode, it remains in command (asynchronous) mode until it makes a synchronous connection with a remote modem. Upon connection, the Courier enters synchronous mode and sends synchronous timing signals to your DTE.
Because the modem will not accept commands when it is in synchronous mode, you will have to configure it in asynchronous mode before trying to connect to a synchronous network.
NOTE: Be sure that DIP switch 1 is OFF (factory setting). The Data Terminal Ready (DTR) override must be OFF so that the Courier detects when the DTE raises and lowers the DTR signal.
To set the modem, follow the instructions for issuing commands in Chapter 4, Command Set Usage. Commands begin with a required AT prefix and end with a required Carriage Return, which we denote with the symbol <Enter>.
For example, the following command causes the modem to set the modulation, the connection rate, and choose a timing source. Spaces have been added only for readability.
