Johnson Controls J2351-IV Intelligent Photoelectric Smoke Detector J5351R it responds to regular polls

it responds to regular polls from the control panel and reports its type and the status (open/ normal/short) of its Initiating Device Circuit (IDC)  Built-in type identification automatically identifies this device as a monitor module to the panel

High noise (EMF/RFI) immunity

The FSP-751 and FSI-751 are also analog devices

Johnson Controls M301MJ is a miniature monitor module that supervises a Style B (Class B) circuit of dry-contact input devices

The FSP-751T photo model includes a built-in thermal (heat) detection device

Johnson Controls J2351-IV Intelligent Photoelectric Smoke Detector J5351R it responds to regular pollsJohnson Controls J2351 IV Intelligent Photoelectric Smoke Detector