Recitaiton room; Teaching room; Class-room; Lecture room

classroom; lecture room; recitation room; teaching room

Classroom;Teaching room;Recitation room;Lecture room

Lecture room; Classroom; Teaching room; Recitation room

Teaching room; Classroom; Recitation room; Lecture room

One class elementary school; One room school; One teacher school; Single room school

one class school; one room school; one teacher school; single room school

One room school; One class elementary school; One teacher school; Single room school

One teacher school; One class elementary school; One room school; Single room school

room in room

room in room structure

Single room school; One class elementary school; One room school; One teacher school

△V detecting

25 Hz phase detecting track circuit

25Hz phase detecting track circuit

ability of detecting earthquake

abnormal detecting

Abnormal detecting rate

Across-zero Detecting