Abstract: A communication system including a fluid-operated calling device mounted in a first location in a building, and a fluid-operated indicator mounted in a second location in a building and in fluid communication with the fluid-operated calling device, wherein actuation of the fluid-operated calling device causes the fluid-operated indicator to provide an indication that the fluid-operated calling device has been actuated. A fluid-operated lock may be mounted near the fluid-operated calling device and in fluid communication with a fluid-operated actuator, wherein actuation of the fluid-operated actuator causes opening of the fluid-operated lock.

Abstract: A sort of tubular door lock whose inside knob or outside knob can be forced to rotate by each other's rotation and force a rotating unit to turn pushing and overpassing a projection of a knocking spring to get the knocking points at its both ends to knock on a bell for ringing. In addition, when said inside knob is locked up, the outside knob has no supporting force for making the latch rotated but can give an idle turning only.

Abstract: An improved knob lock commonly used, which comprises a bell inside. The main part of which is a rotator which is turned by rotating either of the knobs and has two extending-out springs to which are attached a steel ball respectively at their ends. Hindrance rods, which are used to prevent the springs from passing freely, make the springs bend until they are forced past the hindrance rods to knock hard on the bell giving out a ringing sound at the same time.