Image reading apparatus for reading image formed on sheet and image forming system including image reading apparatus

An image forming system connectable to a post-processing apparatus, comprising:

• an image forming unit configured to form an image on a sheet;
• an inspection processing unit configured to inspect the image formed on the sheet by said image forming unit;
• an image reading unit configured to read the image on the sheet conveyed from said image forming unit and configured to transmit image data corresponding to the read image to said inspection processing unit;
• and
• a communication unit configured to output a discharge timing signal, indicating timing when the sheet is discharged to the post-processing apparatus, to the post-processing apparatus through a signal line,
• wherein said communication unit is configured to output the discharge timing signal including a first waveform in a case that the sheet determined to be normal by said inspection processing unit is discharged and is configured to output the discharge timing signal including a second waveform different from the first waveform in a case that the sheet determined to be abnormal by said inspection processing unit is discharged.