14,400 bps modems must connect to computer at 19,200 to 57,600 bps. 28,800 bps modems should connect at a minimum of 38,400 and may go up to 115,200. 16450 UART chips on your IO card can only handle 19,200 bps modem communications. 16550 UART chips can handle up to 115,200 bps depending on computer and modem. This should occur even without a telephone line connected to your modem.
Modems are like computers in some respects.
When they are turned off they lose the active configuration, and when turned back on they must restore an operating configuration into active ram. File transfer problems are often caused by a software or setup problem. If your modem dials and connects but will not transfer files, check your communications program setup. If you are running a Windows communications program, it is important to have your ports set at the proper speed in that program AND in the Windows control panel under ports. The History and Mystery of Modems 14,400 bits per second has been the most common modem speed until recently, and before that 2400 bps was the standard.