Sheet feed device and image forming apparatus

A sheet feed device connected to an image forming apparatus having a first detection unit for detecting a change of state of the sheet feed device, comprising:

• a detection switch unit whose state is switched due to the change of state of the sheet feed device;
• a second detection unit configured to detect a state of the detection switch unit;
• a signal conversion unit configured to convert a detection signal obtained in accordance with a state of the detection switch into a serial signal;
• a communication line configured to connect the first detection unit to the second detection unit;
• and
• a signal line configured to connect the first detection unit to the signal conversion unit,
• wherein when the sheet feed device is in a first state, the first detection unit receives information indicating the state detected by the second detection unit via the communication line, and thereby detects the change of state of the sheet feed device, and
• when the sheet feed device is in a second state, the first detection unit receives the serial signal converted by the signal conversion unit via the signal line, and thereby detects the change of state of the sheet feed device.