Seat belt warning systems in 3rd gens

[Ghoste]

Just trying to educate myself a bit here, but what was the first year for seat belt warning in 3rd gens?  Is it the same each year (assuming more than one), is it a light, a buzzer, both?  Was it sort of hacked in or does it look purpose built?

[Nacho-RT74]

71 got a time delay controlled system warning signal ( just the light ), spliced from same flasher than courtesy light
72/73s are exactly the same between them, controlled by NSS and a relay, linked to retractor and seat sensors. Just a warning signal trigger, and trigs light and buzzer at the same time
74s got the interlock system ( federal cars, not export/canada ), with a central control Unit wich receives NSS, seat and female buckles sensors, and ign switch signals what blocks the starting circuit untill you fasten the seatbelts.

74 Export/Canada got same system but not interlocked. The control unit on these which phisically looks the same just diff color, works like a buzzer and lights warning signals central unit and doesn't affect on starting circuit.

74s got one buzzer for everything controlled by this seatbelt control unit. On A01 package cars the buzzer changes but still being just one piece unit for everything and plugging on same location

Earliers got one diff buzzer for every function.