He should be able to push the button on the pendent to answer his calls.
If you use the receiver, it is like a regular phone and have to answer it as such. The pendent would be better if he shakes.
gotpickled - On the SN6187 - the handset must be picked up to make or answer a call. However, the handset does have a speakerphone features, so your relative can simply press the SPEAKERPHONE button, place the handset down, and have a conversation. Also, consider the SN6197, which has a base speakerphone as well. Thanks!