The DORMA floor spring with electro-magnetic/hydraulic hold-open device with 3.5m cable and cement case.BTS 80 EMB can be used on fire and smoke check doors. The doors must be especially designed for the use with thefloor spring (distance to door hinge pivot 36 mm). An additional approval of suitability in connection with the particular fire and smoke check door is required. For the use on legally approved fire door assemblies, the regulations of the respective notice of approval must be complied with. Fully controlled closing with adjustable speed, a djustable latching action under full hydraulic control, adjustable latching action and backcheck. , m echanical backcheck & h old-open angle range of 75¡ and 180¡ (fall back approx. 3¡).