1. An image forming apparatus comprising:
a first pair of rollers for feeding a print medium;
a second pair of rollers for feeding the print medium, the second pair of rollers being disposed downstream in a print medium feeding direction from the first pair of rollers;
a first detector for detecting the print medium slack in a specified degree by contact with the print medium, the first detector being disposed between the first pair of rollers and the second pair of rollers;
a second detector for detecting either the first pair of rollers or the second pair of rollers need a specified value of driving torque; and
a controller for controlling either a feeding speed at which the print medium is fed by the first pair of rollers or a feeding speed at which the print medium is fed by the second pair of rollers based on either outputs from the first detector or outputs from the second detector;
wherein if the first detector detects the print medium slack in the specified degree earlier than the second detector detects the first pair of rollers or the second pair of rollers need the specified value of driving torque after feeding of the print medium starts, the controller controls the feeding speed based on outputs from the first detector, and if the second detector detects the first pair of rollers or the second pair of rollers need the specified value of driving torque earlier than the first detector detects the print medium slack in the specified degree after feeding of the print medium starts, the controller controls the feeding speed based on outputs from the second detector.
2. An image forming apparatus according to claim 1, wherein the second detector detects the driving torque of one of the first pair of rollers and the second pair of rollers, and transfer of an image is carried out at the other of the first pair of rollers and the second pair of rollers.
3. An image forming apparatus according to claim 2,
wherein the first pair of rollers is to transfer an image to the print medium; and
wherein the second pair of rollers is to fix the transferred image onto the print medium.
4. An image forming apparatus according to claim 1,
wherein that the print medium slacks means that the print medium runs off a plane connecting a nip portion between the first pair of rollers to a nip portion between the second pair of rollers.
5. An image forming apparatus according to claim 1, further comprising a motor for driving either the first pair of rollers or the second pair of rollers,
wherein the second detector detects the driving torque for the first pair of rollers or the second pair of rollers by measuring a current flowing in the motor.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. An intrusion detecting device which comprises:
a plurality of sensor units having a plurality of alert areas defined from a site distant from and to another site near to a subject to be monitored for security purpose and operable to detect an intruder entering any of the alert areas;
a sound generating device capable of generating first and second warnings one at a time, said first and second warnings being different from each other; and
a warning generating unit operable to cause the sound generating device to issue the first warning when detection is made by one of the sensor units, and also to cause the sound generating device to issue the second warning when detection is made by at least another one of the sensor unit during a first predetermined length of time subsequent to the detection by such one of the sensor units.
2. The intrusion detecting device as claimed in claim 1, wherein said sound generating device has an additional capability of generating a third warning that is different from the first warning, and the warning generating unit is also operable to cause the sound generating device to issue the third warning when detection is made only by such one of the sensor units during a second predetermined length of time subsequent to the detection by such one of the sensor units.
3. The intrusion detecting device as claimed in claim 1, wherein said sound generating device has a further capability of generating a fourth warning, and the warning generating unit is also operable to cause the sound generating device to issue the fourth warning when detection is made at least by such another one of the sensor units during a third predetermined length of time subsequent to the detection by such another one of the sensor units.
4. The intrusion detecting device as claimed in claim 2, further comprising a security monitoring camera for monitoring at least portion of the alert areas, and an imaging control unit for activating the security monitoring camera in synchronism with the generation of one of the second and third warning.
5. The intrusion detecting device as claimed in claim 3, further comprising a security monitoring camera for monitoring at least portion of the alert areas, and an imaging control unit for activating the security monitoring camera in synchronism with the generation of one of the second, third and fourth warnings.