A way of connecting more than one computer device to a single control line, such as a line carrying interrupt signals. Only one device contacts the control line directly; the next device contacts the first device, and so on, with all devices forming a single chain. If a device has a request, it blocks any requests from attached devices but sends its own request; otherwise, it passes the request it receives to the device it contacts, or to the control line if it is the first device in the chain.