reel tape, this didnt become the norm  until several seasons into the series. In early episodes, Briggs and  Phelps got their instructions from other sources such as records and  filmstrip projectors. The "tape scenes" for each episode (as they  were known) were usually filmed in one block at the start of each  season. Peter Graves (I) (qv) said he never knew which episode  would use which tape scene until it was broadcast.