Abstract: Systems, devices, methods, and instructions for data communication based on time division multiple access (TDMA), performed by a central office of a network, including identifying a plurality of nodes included in the network, configuring a unit time frame for data communication of the network, such that a plurality of dedicated time slots allocated for data transmission of each of the plurality of nodes and a shared time slot allocated and shared for the data transmission of the plurality of nodes are included, identifying, among the plurality of nodes, a final-stage node predicted to enter a communication-disabled state within a predetermined time period based on status information of each node included the plurality of nodes received from the dedicated time slot, and activating the shared time slot for the final-stage node.

Abstract: A piano tuning pin apparatus for prevention of loosening of the piano string, i.e., of rewinding of a piano tuning pin, characterized by setting the tuning pin constructed additionally a brake structure having the impediment function against the rewinding on the circumference surface of the piano tuning pin and the fixing portion of pin having two putting pipes each other, to prevent loosening of the piano. Between a tuning hammer tip inserting part and a hole of the tuning pin, a brake structure is formed to take a projection having a suitable distance and height along with a circumference surface.