Your problem is that you are trying to connect two FXS devices to each other, which cannot work. An FXS device is one that behaves like the phone company, supplying Dial Tone for outgoing calls and Ring Signal for incoming calls. An FXO device is one that behaves like a telephone set, listening for Dial Tone and responding to Ring Signal.
You need to connect your FXS Dock-N-Talk with an FXO device, like a Sipura
SPA-3000 or a SIPCPE FX-200.