One outdoor unit can have up to around 10 interior units (depending on brand name) attached to it. http://joeun-edu.com/counsel/counsel2.php?BoardID=6&No=290&ProcessValue=VIEW&ListIndexFlag=&KeyField=&KeyValue=&ReturnUrl=http%3a%2f%2fking-Wifi.win%2F%2Findex.php%3Ftitle%3Dbeebemcdonald2718
