So a decade and a half ago there used to be the Google Search Appliance (no idea if it still exists). It was essentially a black (actually yellow) box with some Google magic inside that let you have Google search on premises and for local documents you didn’t want leaving your data center back when people still had their own data centers.<p>One problem with this premise was that when the appliance was not working how it was supposed to, you couldn’t just log into it to fix it because the Google magic was secret. You needed one of their engineers to access it and figure out what’s wrong, but the wrinkle was that every appliance was installed in a different environment and almost certainly behind a firewall that was not easy to open for this process. So to bypass it Google did a very clever thing and added a dial up modem to the appliance. That way you could just go down to the rack, physically connect it to a phone line, and put it into a diagnostic mode where it would dial out to Google to start the remote session. No firewall rules, no unintentional leakage, no accidental logins from who knows where.