Abstract: Circuit for receiving service request signals from peripheral devices in a computer system and providing an address to the computer to effect a program transfer to an appropriate service subroutine. An interrupt request signal is generated to cause the computer to jump to a subroutine. A DMA (direct memory access) request is used to store the address at which the proper subroutine is stored. The proper subroutine depends on the highest priority device supplying a service request signal and on the status of that device. Provision is also made for storing a double-length address.

Abstract: Counter with display devices for exhibiting successive identifiers in response to a change in ambient light such as used in reproducing an image. Each change in ambient light, such as the flash in a photocopying machine or flashbulbs in a camera, increments a counter which is coupled to display devices, which are disposed between the image to be reproduced and the image reproducing means, and which display an identifier corresponding to the number in the counter.