l l l l l l Control section Autoload control and interface circuitry Air-control solenoids Capstan servo control Take-up reel servo control Supply reel servo control CONTROL  SECTION.—  The  control  section provides  the  control  signals  for  manual  operation  of  the MTT.  It  lights  the  MTT  switch  panel  indicators (LOAD,  UNLOAD,  and  STOP)  and  remote  system control panel indicators to notify the MTT operator of operational status. In addition, the control section acts as an interface for MTU control signals and status responses. AUTOLOAD   CONTROL   AND   INTER- FACE.— The autoload control and interface section provides  the  function  signals  for  controlling  the sequential operations of the automatic loading process. It  provides  operator  status  indications  to  the  system control panel and MTT switch panel. It also provides status of the transport to the MTU control unit via the control  section. This  section  also  provides  timing  pulses  and servo-movement  control  signals  to  the  capstan, air-control solenoids, and reel servo-control sections during the autoloading process. AIR-CONTROL  SOLENOIDS.—  The air-con- trol solenoids (Air 1 and Air 2) control the application of vacuum and air pressure during the loading process and during normal operation. Air 1 is energized during the  first  portions  of  the  autoload  operation  to  apply pressure  to  the  buffer  columns.  This  prevents  loops from forming in the columns as tape is fed to the take-up reel. When the tape reaches the take-up reel, Air 2 is energized to apply a vacuum to the take-up reel to cause the tape to adhere to the reel. Once the tape adheres to the take-up reel, then Air 1 and Air 2 are deenergized. When they are deenergized, vacuum is applied to the buffer columns through the vacuum ports. This forms the  loops  of  tape  in  the  columns  for  normal operation. CAPSTAN SERVO CONTROL.—  The  capstan servo-control circuitry controls the direction and speed of the capstan. The purpose of the capstan is to move the tape forward at 120 ips and in reverse at 120 or 200 ips. The 120-ips speed is used for reading and writing in the forward direction and reading in the reverse direction.  The  200-ips  speed  is  used  primarily  to rewind the tape. The capstan is slowed to 120 ips when less than 100 feet of tape remains on the take-up reel (low tape). A special feature allows for fast forward or reverse tape movement (200 ips) under direction of the MTU control unit. The capstan controls tape movement. The reel servo-control systems only respond to or assist in the movement  and  stopping  of  the  tape.  The  capstan  is connected to a tachometer that feeds capstan velocity to the reel servo-control sections. SUPPLY   REEL   SERVO-CONTROL SECTION.— The supply reel servo-control section controls  the  movement  of  the  supply  reel  hub.  Hub motion depends on capstan direction and velocity, reel tachometer input, and vacuum/pressure sensors in the supply buffer column. Four vacuum/pressure sensors are located in the supply buffer column. These sensors (labeled A, B, C, and D in fig. 9-19) locate the tape loop within the vacuum (buffer) column. Sensors B and C are called control  sensors.  During  normal  operation,  the  tape  loop is  between  sensors  B  and  C  in  the  column.  The servo-driven hub attempts to keep the loop between sensors B and C at all times. Sensors A and D are called fault sensors. If the tape loop reaches above sensor A or below sensor D, a fault condition is indicated. A fault condition removes the tape transport ready status and stops tape movement. At the mouth of the supply buffer column(fig. 9-19) is the reel tachometer. The reel tachometer assesses the speed of the tape being fed into or taken out of the supply  buffer  column.  The  speed  of  the  reel  tachometer is compared to the speed of the capstan tachometer. The greater  the  difference,  the  greater  the  change  in  the speed of the servo-driven hub as it responds. TAKE-UP   REEL   SERVO-CONTROL SECTION.—  The  take-up  reel  servo-control  section  is identical to the supply reel servo-control section. CARTRIDGE MAGNETIC TAPE DEVICES Cartridge magnetic tape devices perform the same functions  as  standard  magnetic  tape  unit  controllers  and transports. The cartridge contains a mechanical system of belts, guide rollers, and capstans as shown in figure 9-22. The cartridge is inserted into the applicable unit, which  contains  the  controller  and  the  read/write heads,  drive  roller,  and  sensors  of  the  unit.  The 9-18