NBC Late Night promo, 1983

NBC was having a hard time from 1977 (when "Sanford & Son" ended) and 1984 (when "The Cosby Show" debuted).  In between, there was utter chaos throughout the network, including in its usually strong late night slate: "The Tonight Show Starring Johnny Carson" nearly ended when Carson tired of NBC President Fred Silverman.  Later, he cut his show from 90 minutes to 60, and eventually "Tomorrow with Tom Snyder" was killed in favor of "Late Night with David Letterman."  "The Midnight Special" ended.  "Saturday Night Live" went from juggernaut to reviled after Silverman clashed with producer Lorne Michaels (and Michaels left).  "Second City TV" was brought in -- eyed as a potential, eventual replacement for SNL -- but was canceled after two years.
By 1983, though, things had settled down and were actually thriving.  Johnny Carson was happy with the then-current NBC brain trust (legendary programmers Brandon Tartikoff and Grant Tinker).  "SCTV" was replaced by "Friday Night Videos," produced by Tartikoff's pal, Dick Ebersol.  Ebersol was also producing SNL, which was riding high thanks to Eddie Murphy.  And "Late Night with David Letterman" was the hippest show on TV.
Below is a two-minute promo for the late night shows, likely made for sales/programming use within the network.  But occasionally, it was probably shown during long breaks, rain delays, etc.  This version is localized for WILX-TV (Lansing, Michigan).  Back then, networks routinely made these for their prime time slate, but this is the first one I've ever seen for late night.