The operation console clock button SB2 (X25) sends out the clock signal, triggers the output bit Y12 (K11) output, relay K11 turns on the bell relay KA3, the bell sends out the sound light signal, and the length of the bell corresponds to the clock duration. The downhole dotting button S13 (X25) sends out the doting signal, outputs kr9 through the photoelectric coupling isolation circuit, synchronously inputs PLC input bit X25, and triggers Y12 (K11) to output the electric bell signal. All positions on the ground are directly connected to the bell control point to complete the clock.