Wired Voice and Data to Cellular Options?

otterboy asks: "I am involved with a remote scuba diving operation in Northern British Columbia. The lodge has a regular wired handset, with a wire running up to the top of a nearby mountain. At the top of the mountain sits a little shack, which contains a cell phone, a big antenna, and a black box from Motorola. That box provides an RJ11 jack into which we can plug the 'regular' phone, which allows us to use the cell link from the regular wired phone in the lodge, since the only cell signal we can get is at the top of this mountain. We also use a GSM modem (over the 'regular' phone line, which gets converted to a cell signal up on the mountain), but the best rate we can get is about 4.8kbs. According to Motorola, this is a limitation of their converter. I've looked at Cellsocket, but it deals only with voice. Does anyone know of a converter with better data performance, or are we stuck with Motorola?"