Key telephone system is designed for and marketed to small to medium-sized businesses. It is typically sold to businesses supporting from 5 to 100 users. This system typically similar to Hybrid-key system or PABX system features.

Technically, KTS is a multiline telephone system that provides immediate access from all terminals to a variety of telephone services without attendant assistance.

A feature permitting the user to program a phone to ring at an alternate location; call forwarding may be in effect at all times or just when a particular phone is busy or doesn't answer.

Additional features, like voice mail, automated attendant, automated call directory and a variety of trunking protocols. Most Key systems are capable of linking to E1 and PRI/BRI communications protocols and support loop start and ground start. ETISALAT is using Loop start analogue method for Central Office Connection.

The main features that KTS can provide to the end user are as follows:

Call Forwarding

A feature permitting the user to program a phone to ring at an alternate location; call forwarding may be in effect at all times or just when a particular phone is busy or

Call Hold :

A feature allowing the user to put one caller on hold while other calls are made or answered.

Call Park:

A feature allowing a call for a busy extension to be put into a hold-like state until someone at that extension or another extension becomes free to answer it. The call is brought out of "park" by dialing a special code.

Call Transfer

A feature allowing a call to be transferred to another phone

Call Waiting

A feature that provides audible or visual indicators to let a single-line-phone user know that she has another call waiting for her.

Caller ID

ETISALAT value added service allowing the subscriber to view the phone number of the calling party on a display device before answering the phone. Caller ID usually requires some kind of hardware phone interface to provide the displayed information.