8.11.1.1. Brief Description of Keyset Features 
- Every Keyset has an initial or primary line which is reached via the main station number. This line can be assigned to other Keysets as secondary line.
- A phantom line is assigned to other terminals as a secondary line and is not assigned to any terminal as a primary line. A phantom line is configured as a logged-off Keyset, i.e once the phantom line is configured (SBCSU:ins=signoff) it must be added as a prime line in KCSU to enable it to be added as a secondary line on other Keysets.
- Call: Every line can be configured to be either a line with, or without, ringing (KCSU, RIOP parameter). Ringing tone is activated as soon as a call is signalled on one of the lines for which ringing has been configured for this particular station. The LED of the line key flashes. Several simultaneous calls are signalled in the order of their arrival. Different ringing can be set for all line keys for which the ringing tone has been programmed. If the ringing tone cannot be injected because the Keyset is busy an alerting tone is activated (if configured, KCSU, BUSYRING parameter).
- In case of a Keyset, all parallel ringing features (pick-up group with GRPCAL, ONS group, parallel hunt group etc) use exclusive ringing for the called line, i.e. only the device that has that line defined as primary will ring.
- Line selection: Automatic and manual line selection is available.
- With automatic line selection one of the configured lines is
automatically seized as soon as the user goes off-hook to initiate or
answer a call. Several options can be set defining the preferences of
outgoing and incoming connections.
- Depending on the configured option either the primary line (KCSU, ORLNPF=PRIME), the last used line (KCSU, ORLNPF=LAST), any free line (KCSU; ORLNPF=IDLE) or no line (KCSU; ORLNPF=NONE --> manual selection required) is seized for outgoing connections.
- Depending on the configured option, either a calling line (KCSU; TMLNPF=RING), any incoming line (the calling lines are queried first, followed by lines not set for ringing, on a FIFO basis. KCSU; TMLNPF=ALER) or no line (KCSU; TMLNPF=NONE) is selected for incoming connections. Calls on the primary line can be set to be answered with priority regardless of the time of their arrival (KCSU; TMLNPF=RINGP or ALERP).
- With automatic line selection one of the configured lines is
automatically seized as soon as the user goes off-hook to initiate or
answer a call. Several options can be set defining the preferences of
outgoing and incoming connections.
- Using manual line selection a user can bypass the automatic line selection
by pressing a line key before going off-hook. The options: single key
mode, preselection mode or subsequent line selection can be configured.
- In single key mode (KCSU; SGLBMOD= YES) the line is selected by pressing a line key. The Keyset is switched to hands-free mode with on-hook handset.
- In preselection mode (KCSU; SGLBMOD=NO) the line key is pressed in idle state and the required line is preselected as soon as the user goes off-hook, presses either the loudspeaker, name, DSS or number redial keys or enters dialing digits. The preselection is valid for 10 seconds (configurable via AMO). If a line with ringing has been configured, the calling party is displayed when the line key is pressed until the preselection time expires. After preselection the incoming call can be received on the preselected line by going off-hook.
- Subsequent line selection. The user lifts the handset and presses a line key to subsequently choose or change the line to be used.
- Classes of service: Calls can be initiated using any line on any terminal. Depending on the system configuration, the line COS or the COS of the Keyset is used (AMO ZAND, COSLNBAS parameter). There are, however, features which always use the COS assigned to the used terminal or the used line.
- Display: During the call, and after answering a call, the display of the called party normally displays <Station number and name> of the primary line of the calling station or the used line, depending on the system configuration (AMO ZAND, DISLNBAS parameter). The key also affects the display of the calling party after the B party answers.
- General and exclusive hold. Hold allows a user to hold a connection
and then to go on-hook or to initiate or answer a call on a different
line without losing the held connection. Only two-party calls can be
held. Holding of consultation calls is not possible.
- If general hold is set, the held connection can be picked up by all Keysets where the respective line is assigned (the LED flashes slowly on those stations) by pressing the line key.
- If exclusive hold is set, the held connection can only be resumed by the Keyset which put the line on hold (the LED flashes slowly only on this station) by pressing the line key.
There are three ways to put a line on hold: by pressing either the "Hold" or "Exclusive hold" keys or by selection from the dialog menu. Changing to another line or pressing the line key of the current line also puts a line on hold (or releases it, depending on the system configuration, AMO ZAND, HDNOACKY parameter).If exclusive hold is set, the Keyset which put the line on hold receives a recall with priority, if the held line is not resumed after the timeout. If general hold is set, a recall is signalled at all Keysets where the line is assigned. - Multiple consultation. A user with several assigned lines can initiate a three-party conference by pressing the line key of the line he wishes to override. A three-party conference is established, if a two-party call (A-B) is active on the selected line and no private call has been initiated. Conference tone is injected at all three parties (A, B, C) if multiple consultation is activated. Only one station can enter into an existing connection.
- Private call. This feature protects the Keyset user against multiple consultation by another Keyset user. Automatic and manual private calls are possible. Automatic private call (configured using AMO KCSU, APRIVAT=YES) is activated as soon as a call is initiated. Keysets without the automatic private call feature are protected for one connection by activating the feature manually.
- Display of seized line. The line currently seized or selected by the Keyset is displayed, as soon as the handset is lifted. Automatic display of the currently seized line is activated as soon as a line is selected. The currently used line can be queried manually in various states via the function key "I-USE" or selection of the menu "Show seized line?" in the service menu.
- Ringer cut off. The user can deactivate ringing at the Keyset by pressing the "Idle" key or selecting "Switch off ringing?" in the service menu. The LED of the corresponding function key is "on" if this feature is activated. Incoming calls are only signalled optically by the flashing LED on the line key(s). All incoming calls are signalled at their required destination, but only visually (LED, display). They can be answered as usual. Some call types override Idle, e.g. exclusive calls, ACD.