You may want to "park" a current call by disconnecting from the peer without breaking the call. Later you can reconnect to the peer (to "pick up" the call), using the same or a different phone or device.
To park a call, use the phone "blind transfer" function to transfer the peer to the *55 number. The peer will be connected to a service application playing music-on-hold, and your device will be disconnected.
To pick up a call, dial the *57 number from any of your own devices. The service application finds your parked call and connects you to the peer.
You may want to use any device to pick up your parked call. Dial your own number to connect to your voicemail application and use the Access PIN feature to access your service application. Then enter the 57 code to pick up the call.
You can park several calls at the same time. When you pick up the parked calls, they are retrieved in the same order they were parked.
You may want not to send music-on-hold to a parked call (for example, when you park a conference call with active participants). Blind-transfer a call to the the *56 number for "silent parking".
If you dial the *55 or *56 number, your own call will be parked. You can use your other device to pick up this call, establishing a call between your own devices.
A "parked peer" can press the # button to disconnect.