A spell checking system includes a letter spelling engine. A controller may maintain a register with requirements for accessing particular memory locations to initiate a security protocol. Accordingly, since it is possible to alternately supply the sheet-like optical discs in which both surfaces are recorded and reproduced to the A-side and B-side recording and reproducing apparatuses from the cartridge, it is possible to record and reproduce continuously and in parallel. A preferred construction of the mixer is also described. A linear damper is operatively connected to the first linkage at a distance from the pivot point, such as by a second linkage or lever arm, and connected to the base for damping pivoting motion of the first linkage. The system includes an RFID antenna positioned about the E-Z pass express checkout lane for communicating with an RFID transponder issued to a preferred member when the RFID transponder is in close proximity to the RFID antenna.