With HFC connections, your service provider is usually the organisation that supplies the access network, i.e. they supply the utility box on your external wall, as well as the gateway modem (often called a 'cable modem', but identical in function and purpose), but there is no NTD or power supply/battery backup equipment – just a wall outlet and internal cable.
When your fast broadband is provided via HFC, your telephone service will usually continue over your existing copper wire connection. There are exceptions to this, e.g. where a Voice Over IP (VOIP) service is used, in which case the telephone service will be provided via one of the data ports on the gateway modem.