The Streamer can be “paired” with multiple phones & Audio Sources. (I can’t remember how many but if you exceed the number of devices, it will over-write the oldest).
BUT…
Only one phone and One Bluetooth Audio Streaming Device can be active simultaneously. Your Palm & the Plantronics are both using handsfree profile and only one could be the “active” connection for phone at a time. Switching between them automatically is not possible unless they were located outside the BT range from each other. (same holds true for 2 BT Audio sources) switching is done manually unless they are far apart.
General Info…
There are 2 types of bluetooth profiles in the Streamer. One is the handsfree profile and it is used for phone calls, the other is A2DP which is used for streaming audio. (MP3 etc.) If you wanted to, you can have a 3rd device active by using the plug connection.
Streamer will automatically prioritize the use of the devices based on what they are and what their transmission status is. If you are listening to music (either corded or A2DP) and the phone (Hands Free) rings, it switches to the phone mode.
In order to be connected to 2 phones simultaneously (ie. cell & office desk phone), you would have to use a Bluetooth phone hub (I think Jabra & Plantronics have them). In that case, you pair the streamer to the hub and make that connection active. The hub is used to switch between the cell or the desk phone. (I have not yet tested it but that is how it works in theory)
Another way to have both cell & desk phone simultaneously is to replace the desk phone with a bluetooth enabled phone that is linked to your cell. AT&T, Panasonic & V-Tech have these types of phones. (Siemens has some too but they don’t seem to be available in the US.) In this setup, The Cell is linked to the Base unit of the Desk phone & the Streamer is linked to the base unit of the desk phone.