Abstract: A composite shift register timer for controlling a sequence of events occurring over a demand-response interface. The composite shift register comprises a primary shift register and a secondary shift register. The primary shift register is divided into successive portions which are selectively coupled together in successive pairs upon timely receipt of respective response signals. A first binary "1" is inserted into the first portion at the start of a predetermined sequence of events. The first "1" is clocked through to the end of the first portion where it initiates a demand and is stored pending the receipt of a corresponding response. A second binary "1" is clocked through the secondary shift register beginning with the initiation of each demand. The clocking of the second "1" continues until the receipt of a timely response to the initiated demand whereupon the secondary shift register is reset.