One of methods to communicate with the controller if distance exceeds 15 meters (also connecting two computers to transfer files at significant distances) is by means of a direct modem to modem connection. The only thing necessary for a reliable connection of this type is a "Phone line simulator", a device to provide simulation of a telephone line, supplying the line current that modems are designed to work with. For these purposes, a very simple circuit will do the job. It is connected between two telephone modular jacks, and the two modems plug into the jacks.
Phone Line Simulator SP2
SP2 Basic Circuit
SP2 Electronic Circuit
WARNING: RST is not responsible
for any damage caused by connecting to SP2
power supply unit (or any other devices), which have different specifications
as recommended by RST. Standard
adapter +7.5V (300 mA) is recommended for SP2.
