Black Box MD1640A Terminal Emulation, File Transfer Protocols, When to Disable Data Compression

User Guide for Series II Modems

3.6.2 Terminal Emulation

If you are accessing the remote computer as if from an on-site terminal, the keyboard codes used by your computer may not match the ones used by the remote computer. To be compatible with the remote com- puter, your software must be able to substitute the appropriate codes in what is known as terminal emulation. Most communications programs can emulate the most common mainframe terminals, including the DEC VT100, VT102, and VT52 terminals, and the basic TTY mode. If in doubt about which to choose for a Telnet session, a BBS connection, etc., try ANSI or VT100 first.

3.6.3 File Transfer Protocols

When you upload or download files with your Series II Modem through a browser, it will transparently use the appropriate protocol (usually http or ftp). When you are uploading or downloading through a terminal emulator, however, the host computer will ask which file transfer protocol you want to use. Most communications programs allow you to choose a default protocol. Your software’s documentation should list the ones it can use (not all communications programs support all protocols). Zmodem is the recommended protocol for most transfers.

3.7 When to Disable Data Compression

If your serial port cannot keep up because it has an older UART, you may lose data when using data compression. Also, the speed advantage hardware compression gives you is entirely dependent on how much the data being transmitted can be compressed. If the data is already in compressed form—a .ZIP or a .SIT file, for example—trying to com- press it more will actually slow the transmission slightly compared to transmitting the same file with compression disabled. This effect will be most noticeable if your modem negotiates MNP 5 compression with the other modem. V.42bis will not try to further compress a compressed file, but MNP 5 will.

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