core/homeassistant/components/voip/strings.json

{
  "config": {
    "step": {
      "user": {
        "data": {
          "ip_address": "IP Address"
        }
      }
    },
    "abort": {
      "single_instance_allowed": "[%key:common::config_flow::abort::single_instance_allowed%]"
    },
    "error": {
      "invalid_ip_address": "Invalid IPv4 address."
    }
  }
}