TURN server is strictly required or optional?

just to make sure, TURN server is strictly required or optional? And one question more, in wiki i saw explanations how to set TURN server settings, but never for signaling server. Do we need to set somewhere something like:
window.ua = new SIP.UA({
traceSip: true,
uri: 'bob@example.com',
ws_servers: ['wss://sip-ws.example.com'],
mediaHandlerFactory: PhoneRTCMediaHandler
});
and window.ua.on('invite', makeCall) ?
I have freeswitch as signaling server, will it work without TURN server?
P.S. trying to run https://github.com/alongubkin/phonertc/tree/master/demo/client