respectively is routed through the mac to the 1 out jack when switch 5 is in position s1 otherwise the 1 out and selected signals are equal the router can therefore route signals from the c in 1 in or k in jacks through the mac for the desired address conversion turning now to the mac its block diagram fig1 will be considered first followed by the details of each block serial data from the router after conversion to parallel data by uart 50 appears on data bus d1 d8 as byte d input to adder 51 and controller 52 the amount to be added or subtracted to a midi address is input to the adder as byte q from the increment selector 53 via bus q1 q8 byte b output by the adder to the uart via bus b1 b8 depends upon the logic state of control lines c1 and c2 if c1 c2 1 1 then b d if c1 c2 0 1 then b d q if c1 c2 1 0 then b d q 1 byte b is converted to serial data by the uart and sent back to the router the controller receives information about the sign of the increment via control line c3 on which the voltage is high for plus and low for minus referring to the control lines between the uart and the controller dav stands for data available tbmt stands for transmitter.