PURPOSE: To enable a limit signal to be transmitted in a reduced number of cables by making a change into a code which is in accordance with the combination of the output signal conditions of respective limit switches and conducting sending out to cables whose number is the same with that of the bits of this code, and afterward, decoding these output signal conditions at the receipt of the code having been transmitted via cables.

CONSTITUTION: In case of a limit signal having been outputted from a limit switch 1, respective output signal conditions 'PCM' of respective limit switches 1-3 become 'HLL'. As a result, at a coder 4, the output level of its OR gate 5 becomes 'H' and at the same time, the output level of an OR gate 6 becomes 'L'. Accordingly, the encoder 4 sends out codes 'HL' to respective cables 7, 8. Meanwhile, at a decoder 9, when these codes 'HL' are inputted, the output PL alone of an AND gate 10 becomes an H level, and thus, codes 'HLL' that show a limit has been detected by means of the limit switch 1 are sent to a manipulator controller main body 13.