A door safety circuit for monitoring of story doors in lift installations. The door safety circuit includes a transmitter that produces a non-electrical signal which is guided by a series of conductor portions. The non-electrical signal may be transmitted through a first conductor partial portion to a latching device of a first story door, depending upon the latched state of the first story door, the signal may be either transmitted to a second conductor partial portion, which may be included within the latching device, or no longer transmitted. If the signal is similarly transmitted through a plurality of conductor partial portions and serially connected story door latching devices, the circuit may indicate that each story door is properly latched. The circuit may also include a plurality of sensors coupled to a failure recognition circuit for monitoring each conductor partial portion.