Sony MDR-1RBT - Manual (Page 67)

Tip
With an HFP connection, you can call in the following way, depending on the
smartphone or mobile phone. Refer to the manual supplied with your
smartphone or mobile phone for the details of the operation.
When not talking, you can call using the voice dial function by pressing the
button.
You can call the last dialed number by pressing the button for about 2
seconds.
Note
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