E-mail from Telstra advising of planned outage. This sort of thing does not really effect us any more as the Telstra Smart Modem Gen 2 has 4G backup – including voice

Your Telstra service on the NBN network may be interrupted for up to 1 hour on 23 April 2019 between 10:00pm and 5:00am, as maintenance is scheduled to be performed by NBN co in your area. The service disruption will include calls, if you need to make emergency calls (000), please use your mobile or an alternative option.