The fifth ARPANET IMP was installed at BBN in early 1970; once it was in place all the IMPs sent periodic status reports to the IMP 5 “console,” a Model 33 Teletypewriter (10 characters/second). Bernie Cosell recalls: “I was mostly the guy reading the TTY output at that time. But as the net grew, that was getting to be harder and harder (too damn much paper clanking away in the back room). There was a spare [Honeywell] 316 in the room next to the PDP-1, and we got some kind of fairly-high-speed printer for it [Model 35 Teletype – 15 characters/second]. So it [the Honeywell 316] first came up just as a network host and just printed out all the junk on the nicer printer. But I added a bunch of smarts to it. In particular, I kept track of things and only reported changes (who was up, who was down, some heuristics for when a report was overdue). Then Jon Cole cobbled up a lights box [which displayed IMP status or circuit status on a set of 32 lights] and then the 316 was modified to signal an alert and flash appropriate lights. Another thing I did was to put in ‘topology’ code -- so that if, say, imp 5 went down, it would figure out that we had no reporting-path to imp 6 and put it in a (quiet) limbo instead of announcing that it was down. This proved to be useful for other similar things; when a line went down and segmented the net, the code was smart enough to report ‘either this IMP or this line is down’ and not list another 20 IMP Down reports.”