Method of displaying caller identification for abandoned call in key-phone system

A caller identification display method in a key phone system including a key service unit and a plurality of extension line subscriber terminals, said method comprising the steps of:

• generating a ring signal from said key service unit to a designated extension line subscriber terminal in response to reception of an incoming call from an office line;
• storing caller identification information contained in said incoming call during a pause period of said ring signal, in a temporary buffer;
• sequentially registering the caller identification information stored in said temporary buffer in a predetermined region of a caller identification abandon buffer, when an office line caller terminates said incoming call;
• and
• providing a visual display of registered caller identification information on the designated extension line subscriber terminal, in response to depression of a caller identification key.

A key phone system, comprising:

• a key service unit having a plurality of first ports coupled to a plurality of office lines and a plurality of second ports coupled to a plurality of extension line subscriber terminals, each terminal including a handset, a display unit for providing a visual display of caller identification information, a plurality of discrete function keys including a clear key, a scroll key, a dial key, volume-up and volume-down keys, a caller identification key and an end key, and a plurality of alphanumeric keys for inputting a telephone number;
• and
• said key service unit including a memory for storing said caller identification information, and a controller for controlling registration of caller identification information of each incoming call by:
• sending a ring signal to a designated extension line subscriber terminal in response to reception of an incoming call from an office line;
• registering caller identification information included in said ring signal during a pause period of said ring signal, in said memory;
• after said caller identification information is registered in said memory, requesting a password from a subscriber from the designed extension line subscriber terminal for access to said caller identification information registered in said memory, when said caller identification key is depressed by the subscriber from the designated extension line subscriber terminal;
• and
• when the password input from the designated extension line subscriber terminal is accepted by said key service unit, providing a visual display of registered caller identification information on the display unit of the designated extension line subscriber terminal.