Analog Phones like the Polycom SoundStations have only limited functionalities to enable/disable certain features on a PABX / PSTN Line.
The Phones uses the Conference / Join Button to send a Flash Signal to an analog Line.
The Flash actually interrupts the Phone Line for a pre-defined duration and signals to the PABX / PSTN that a feature is requested.
NOTE: This functionality depends completely on the PABX / PSTN.
Usually this is used to place the call on hold and the PABX / PSTN will provide a new Dial Tone and enable the user to call another Phone or retrieve the call from hold if pressed again.
NOTE: Please be aware that a limitation may be that the analog line does not support a 2nd Call. Please liaise with your PABX / PSTN Provider.
Most Polycom SoundStations offer a Menu Option that can change the Flash time.
A usual Value depending on the PABX / PSTN would either be 75ms, 100ms, 300ms or 600ms.
Certain PABX / PSTN require a "*" start or "#" hash/pound code with or without additional numerical digits to invoke the Conference facility and need to be manually dialed.