SIP telephones and SIP softphones generally feature special keys or menu entries to manage calls. Different terms may be used depending on the model or software program, but the functions are as follows:
- CALL HOLD: Places an active call into a wait mode or swaps between two active calls. On ISDN and analog telephones this function is often referred to as the F-key/Flash/Call hold. Flash function (F key).
- HANG UP: End the current call.
- SWAP: Swap between two active calls (depending on the ISDN telephone, this may be initiated by a display-menu entry, a special key, or the "F" key).
- TRANSFER: Initiates the call forwarding (can be triggered by "hanging-up" with an active call and a call on hold)*.
These functions can be used to manage calls as follows:
| Holding/consulting and continuing with calls | SIP | ISDN | Analog |
|---|---|---|---|
| To place a call on hold, press the Flash/Call hold key (or 'F' on analog phones). The caller can no longer hear you and you can initiate a second call by dialing a telephone number (consulting). | CALL HOLD | HOLD or F | R |
| To continue with a call which is on hold, press the Flash/Call hold key again (or 'F 2'). | CALL HOLD | HOLD or F | F 2 |
| If the consultation call has not yet been picked up, you can stop the consulting by hanging up the handset on a SIP or ISDN telephone*. You can stop the consultation call with the appropriate menu function of the telephone (e.g. 'Cancel') or 'F 1' (analog).* | HANG UP | HANG UP | HANG UP |
| Swap | SIP | ISDN | Analog |
|---|---|---|---|
| To open a second line during a call, first press the Flash/Call hold key (or 'F' on analog phones). The other caller can no longer hear you. | CALL HOLD | HOLD or F | R |
| Dial the number for the second caller while the first call is on hold. If you cannot reach the second caller, you can return to the call which is on hold by pressing the hold key (or 'F' on analog telephones). | 123456789 | 123456789 | 123456789 |
| As soon as two simultaneous connections are open, you can use the hold key (or swap key for ISDN phones, 'R' and '2' for analog phones) to swap to-and-fro between the two connections. You will be connected to one of the other callers; the other caller is placed on hold. | CALL HOLD | SWAP | F 2 |
| To end an active call, hang up the handset on SIP or ISDN telephones, and on analog phones press 'R 1'. The call which is on hold is not automatically reactivated, but it will be signaled (ringing phone) for a period of 15 seconds. | CANCEL or HANG UP* | CANCEL or HANG UP* | F 1 |
| Call forwarding, consult | SIP | ISDN | Analog |
|---|---|---|---|
| To open a second line during a call, first press the Flash/Call hold key (or 'F' on analog phones). The other caller can no longer hear you. | CALL HOLD | HOLD or F | R |
| Dial the number for the second caller while the first call is on hold. If you cannot reach the second caller, you can return to the call which is on hold by pressing the hold key. | 123456789 | 123456789 | 123456789 |
| As soon as you have established two simultaneous connections you can connect the two callers with the connect key (or 'F' and '4' on analog phones) or by hanging up the handset.* Optionally you can switch between the two lines as often as you like before transferring the call. Call transfer always connects the active call and the call on hold. | TRANSFER or HANG UP* | TRANSFER or HANG UP* | R 4 or HANG UP |
| You have no more active calls. You can either hang up or make a new call. | HANG UP 123456789 | HANG UP 123456789 | HANG UP 123456789 |
| Call transfer, blind | SIP | ISDN | Analog |
|---|---|---|---|
| To open a second line during a call, first press the Flash/Call hold key (or 'F' on analog phones). The other caller can no longer hear you. | CALL HOLD | CALL HOLD | HOLD or F |
| Dial the number for the second caller while the first call is on hold. | 123456789 | 123456789 | 123456789 |
| Press the connect key (or 'F' and '4' on analog phones) or hang-up the handset before the second connection has been established.* The two callers will now be connected "in the background". | TRANSFER or HANG UP* | TRANSFER or HANG UP* | R 4 or HANG UP |
| You have no more active calls. You can either hang up or make a new call. | HANG UP 123456789 | HANG UP 123456789 | HANG UP 123456789 |
Note: (*) In some cases, SIP or ISDN telephones can be configured so that hanging-up the handset either causes the consultation or active call to terminate, or a call forwarding is triggered ("Transfer").
