An old rotary phone as Bluetooth set

When did the charm of holding a bulky receiver to your ear end? What if we could bring the feel of the old times to our smartphones?

Xabi Z

Quantity		Component name
1	×	USB Sound-card A cheap USB-Sound card with microphone and speaker connectors
1	×	Raspberry Pi Zero W With built in Bluetooth and Wi-Fi!
1	×	OTG Cable To be able to connect the USB Sound-card to the Raspberry Pi Zero W
1	×	An old rotary phone In my case a FeTAp-611 phone acquired on E-Bay
1	×	USB Power supply Either a cable to a socket-charger or a power-bank will do the job