PURPOSE: To make output a jam detection signal by sampling a hole position at a normal time and a hole detection signal of every hole position with clocks and by comparing this signal with a sampling signal slided by one clock.

CONSTITUTION: Paper 1 has many holes at both ends between which the opposite and coupled light transmitter and light receiver are established. A sampling sircuit 12 is sampled by a clock CLK which syncronizes with a signal Sg and cycles at 1/2 of the cycle T of the signal. 13 is a memory circuit and 14 is an encounter circuit. When paper stops at a arrow mark the paper 1 cuts light 5 and after the paper stops the signal Sg1 does not become a H level like a signal Sg2. And an output signal Sp3 of the encounter circuit becomes the H level at each clock timing. Thus, paper jam detection signal output.