VB 26: Sequence control register nickle delay line (19 digit). VB 27: B register used in control unit (22 digits). [Added on 2-8-2008] TN7 unit. VB26: Sequence control register nickel delay line. 19 digit delay using ultrasonic magnetostrictive effect. VB27: B register used in the control unit. 22 digit delay using nickel magnetostrictive delay line.