Incoming calls to the user alert on all their devices and they can choose which device they want to use to answer.

Whilst the user has a call in progress on one of the devices, any additional incoming call is presented only to that device.

It is recommended not to mix simultaneous mode operation with features such as mobile twinning, telecommuting and mobile call controls that can lead to multiple duplicate calls. For example, a mobile client's external PSTN numbers as a active mobile twinning destination will cause duplicate alerts for the same call.

Users can have their desk phone and their softphone applications registered to different servers in an IP Office network.

Use of simultaneous mode is not supported when also using a non-telephony CTI client to control call handling. In that scenario it is not always possible to predict which telephony client will be used when making/answering a call from the CTI client which can lead to confusion.