Figure out how many extensions you need. Consider both today's needs and tomorrow's expansions. Instead of giving one dedicated line to each phone, everyone gets an extension and shares a handful of outside lines. To dial within a company, one just dials an extension. To dial out, one usually dials 9 first.
Many companies share just a few regular phone lines among several employees.
Incoming calls go to a receptionist who puts the caller on hold and tells the recipient which line to answer. Hybrid systems combine features of both PBX and KTS systems. Server-based systems are great for those who want to merge phones and PCs. Instead of buying traditional PBX, KTS or other equipment, phones and lines connect to a computer that manages calls. Automated call distribution answers incoming calls, queues them and tells callers to hold until someone is available to speak to them.