The IGM 500 system of the early 1970s used a proprietary MOS circulating memory in a controller that handled their Instacart, and could program break sequences. The schematic for the memory controller could cover a large wall. Each step of the "program" included a tray number and a single digit that chose between the next controller step in the sequence, or a return to the music sequencer. The system used a simple stepper relay sequencer to establish music deck rotation, each step programmed with a thumb-wheel switch. Logging information was a set of 5 DTMF bursts on the cart cue track that were decoded and printed on a paper tape along with the time of day. All the electronics were completely proprietary. Even the time clock was a proprietary set of boards made up of TTL counters and 7 segment decoder-drivers. All digital displays were RCA Numitron hot filament numerics. Yes, segments did burn out. They made the logging tone burst encoder too, and silence sensor...probably the most important bit of the whole beast. When the memory controller messed up it would fire a bunch of carts in rapid sequence, almost at once, and since there was only one output from an Instacart, you got them all on the air simultaneously, where they played until either an EOM tone was detected, or enough trays were started to stall a capstan motor (12 carts per motor, 48 carts, pinch rollers, and heads total).