Type of smoke/fire detector???

Can anyone tell me more about this device that was located in basement above and near furnace. See photo of front and partial of rear. Thx.



**Wind up Vanguard Thermosonic heat detectors.

Thank you. Looked it up on web and found more info.

They were expensive units at the time. Somewhere around $800 if I remember correctly. I sat through one of their in-home presentations and finally threw the guy out when he tried certain high pressure sales techniques. That was 1980 or '81 I think.

The Consumer Product Safety Commissionhad this to say…