One base can fit to 999 Calling set ( if is need) Frequency:315/433 Mhz Distance is about 100 M (more range is depended on you We sell cordless calling system for restaurants, coffee shop, night club, supermarkets, shopping mall, store,hospital, product line, sports center, bowling lane, golf course, bank and so on.we have different models. One base can fit to 999 Calling set ( if is need) ...