It sounds like a silent alarm which was common in the 60's in buildings of public assembly, Theatres, Cinemas and occasionally large Departmental Stores. If a fire was discovered by the staff they informed the manager or the store PBX and they initiated the silent alarm which informed all the staff in the building of a possible fire in the building. A common method was the fire record, quite often "Colonel Bogy". One store I was aware of was Bins formally known as Henderson’s which had clocks visible throughout the store with a light above each number. It was used as a paging system and when all the lights were illuminated this indicated a fire alarm which required all the staff to follow a set procedure. If after a set period of time the manager or the telephone operator did not receive a call cancelling the alert then the fire alarm went into the full general alarm, in stores this was by operating the sounders usually automatically.
As for not seeing any AutoFA this was the norm except in hotels because MoE was always achieved by passive methods and active methods was only used when it was impossible to achieve a satisfactory MoE using passive methods. With a full sprinkler system then installing AutoFA would have been very unlikely
As for not seeing any MCP’s the fire alarm would be controlled at the store PBX.
As for the sounders, I cannot explain, other than to suggest they where hidden or they had adopted the system used in Theatres and Cinemas which would have been unusual.
