1. (canceled)
2. A display device comprising:
a first transistor in a pixel portion over a substrate;
a driver circuit over the substrate and electrically connected to the first transistor;
a protection circuit electrically connected to the driver circuit, the protection circuit comprising a second transistor, wherein each of the first transistor and the second transistor comprises an oxide semiconductor layer over the substrate, a gate insulating film over the oxide semiconductor layer and a gate electrode over the gate insulating film, the oxide semiconductor layer comprising a source region, a drain region and a channel formation region between the source region and the drain region; and
a pixel electrode electrically connected to one of the source region and the drain region of the first transistor,
wherein the source region and the drain region have a lower resistance than the channel formation region, and
wherein the gate electrode of the second transistor is electrically connected to one of the source region and the drain region of the second transistor.
3. The display device according to claim 2, wherein the source region and the drain region are doped with a metal element.
4. The display device according to claim 2, wherein the source region and the drain region are doped with an impurity.
5. The display device according to claim 2, wherein the oxide semiconductor layer is formed on an insulating film having an average surface roughness of less than or equal to 1 nm.
6. The display device according to claim 2, wherein the oxide semiconductor layer has a crystallinity.
7. A display device comprising:
a first transistor in a pixel portion over a substrate;
a driver circuit over the substrate and electrically connected to the first transistor;
a protection circuit electrically connected to the driver circuit, the protection circuit comprising a second transistor, wherein each of the first transistor and the second transistor comprises an oxide semiconductor layer over the substrate, a gate insulating film over the oxide semiconductor layer and a gate electrode over the gate insulating film, the oxide semiconductor layer comprising a source region, a drain region, a channel formation region between the source region and the drain region, a first impurity region between the channel formation region and the source region, and a second impurity region between the channel formation region and the drain region; and
a pixel electrode electrically connected to one of the source region and the drain region of the first transistor,
wherein the source region and the drain region have a lower resistance than the channel formation region,
wherein the first impurity region and the second impurity region have a lower resistance than the source region and the drain region, and
wherein the gate electrode of the second transistor is electrically connected to one of the source region and the drain region of the second transistor.
8. The display device according to claim 7, wherein the source region and the drain region are doped with a metal element.
9. The display device according to claim 7, wherein the source region and the drain region are doped with an impurity.
10. The display device according to claim 7, wherein the oxide semiconductor layer is formed on an insulating film having an average surface roughness of less than or equal to 1 nm.
11. The display device according to claim 7, wherein the oxide semiconductor layer has a crystallinity.
12. A display device comprising:
a first transistor in a pixel portion over a substrate;
a power supply line over the substrate;
a protection circuit electrically connected to the power supply line, the protection circuit comprising a second transistor, wherein each of the first transistor and the second transistor comprises an oxide semiconductor layer over the substrate, a gate insulating film over the oxide semiconductor layer and a gate electrode over the gate insulating film, the oxide semiconductor layer comprising a source region, a drain region and a channel formation region between the source region and the drain region; and
a pixel electrode electrically connected to one of the source region and the drain region of the first transistor,
wherein the source region and the drain region have a lower resistance than the channel formation region, and
wherein the gate electrode of the second transistor is electrically connected to one of the source region and the drain region of the second transistor.
13. The display device according to claim 12, wherein the source region and the drain region are doped with a metal element.
14. The display device according to claim 12, wherein the source region and the drain region are doped with an impurity.
15. The display device according to claim 12, wherein the oxide semiconductor layer is formed on an insulating film having an average surface roughness of less than or equal to 1 nm.
16. The display device according to claim 12, wherein the oxide semiconductor layer has a crystallinity.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A magnetic tape unit comprising:
a magnetic head for reading and writing data from and onto a magnetic tape;
driving means for traveling said magnetic tape kept in contact with said magnetic head during a readwrite operation of said magnetic head;
means for performing a reciprocating motion of said magnetic tape by a small distance with a predetermined period during a rest period where the readwrite operation of said magnetic head is not performed;
a temperature sensor for detecting a temperature in the vicinity of said magnetic head; and
control means for changing said predetermined period of said reciprocating motion according to said temperature detected by said temperature sensor.
2. A magnetic tape unit according to claim 1, wherein said control means reduces said predetermined period of said reciprocating motion when said detected temperature is higher than or equal to a reference temperature.
3. A magnetic tape unit according to claim 1, further comprising:
a fan for ventilating said magnetic tape unit; and
means for changing a rotating speed of said fan according to said detected temperature.
4. A magnetic tape unit comprising:
a magnetic head for reading and writing data from and onto a magnetic tape;
driving means for traveling said magnetic tape kept in contact with said magnetic head during a readwrite operation of said magnetic head; and
control means for changing a tension of said magnetic tape during a rest period where the readwrite operation of said magnetic head is not performed.
5. A magnetic tape unit according to claim 4, further comprising a temperature sensor for detecting a temperature in the vicinity of said magnetic head, wherein said control means changes said tension according to said temperature detected by said temperature sensor.
6. A magnetic tape unit according to claim 5, wherein said control means reduces said tension when said detected temperature is higher than or equal to a reference temperature.
7. A magnetic tape unit according to claim 5, further comprising:
a fan for ventilating said magnetic tape unit; and
means for changing a rotating speed of said fan according to said detected temperature.
8. A magnetic tape unit comprising:
a magnetic head for reading and writing data from and onto a magnetic tape;
driving means for traveling said magnetic tape kept in contact with said magnetic head during a readwrite operation of said magnetic head;
a temperature sensor for detecting a temperature in the vicinity of said magnetic head; and
means for canceling the contact between said magnetic tape and said magnetic head when said temperature detected by said temperature sensor is higher than or equal to a reference temperature.
9. A magnetic tape unit according to claim 8, further comprising a guide for forming a travel path of said magnetic tape, wherein said canceling means comprises means for displacing said guide.
10. A magnetic tape unit according to claim 8, further comprising a pin provided on one side of a travel path of said magnetic tape where said magnetic head is provided, wherein said canceling means comprises means for displacing said pin.
11. A magnetic tape unit according to claim 8, further comprising:
a fan for ventilating said magnetic tape unit; and
means for changing a rotating speed of said fan according to said detected temperature.
12. A magnetic tape unit comprising:
a magnetic head for reading and writing data from and onto a magnetic tape;
means for making constant contact of said magnetic tape with said magnetic head;
a reel motor for traveling said magnetic tape kept in contact with said magnetic head; and
means for driving said reel motor at regular intervals of time to intermittently move said magnetic tape in one of a winding direction and a rewinding direction, during a rest period where a readwrite operation of said magnetic head is not performed.
13. A magnetic tape unit comprising:
a magnetic head for reading and writing data from and onto a magnetic tape;
means for making constant contact of said magnetic tape with said magnetic head;
a reel motor for traveling said magnetic tape kept in contact with said magnetic head; and
means for slowly driving said reel motor to travel said magnetic tape at a speed lower than a normal traveling speed for a readwrite operation of said magnetic head, during a rest period where the readwrite operation of said magnetic head is not performed.
14. A magnetic tape unit having means for loading and unloading a magnetic tape, comprising:
a magnetic head for reading and writing data from and onto said magnetic tape loaded;
means for making constant contact of said loaded magnetic tape with said magnetic head;
a reel motor for traveling said magnetic tape kept in contact with said magnetic head; and
means for measuring an elapsed time from the start of a rest period where a readwrite operation of said magnetic head is not performed after loading said magnetic tape, and for rewinding said magnetic tape to unload it.
15. A magnetic tape unit adapted to use a magnetic tape cartridge having a leader block mounted at a leading end of a magnetic tape, comprising:
a magnetic head for reading and writing data from and onto said magnetic tape; and
a tape threader for performing a thread operation that said leader block is drawn from said magnetic tape cartridge to bring said magnetic tape into contact with said magnetic head, and for performing an unthread operation reverse to said thread operation;
said tape threader comprising: a threader pin for engaging said leader block to move it;
an arm having one end at which said threader pin is fixed, for moving said threader pin;
a support block fixed to the other end of said arm;
a threader motor for driving said arm; and
a transmission gear rotatably supported to said support block, for transmitting a driving force of said threader motor to said support block;
said transmission gear having an elongated hole;
said support block having a pin corresponding to said elongated hole;
said pin being loosely engaged with said elongated hole so that a play is created between said transmission gear and said arm.
16. A magnetic tape unit according to claim 15, wherein said tape threader further comprises:
a first position sensor for detecting a tape thread start position of said arm;
a second position sensor for detecting a tape thread end position of said arm; and
a home position sensor for detecting a home position of said arm;
said first position sensor, said second position sensor, and said home position sensor being mounted on the same board.
17. A magnetic tape unit according to claim 15, further comprising:
a machine reel having a recess for receiving said leader block, for winding said magnetic tape;
means for driving said threader motor to move said arm, so as to engage said leader block into said recess of said machine reel; and
means for driving said threader motor to slightly move said magnetic tape after said leader block is engaged into said recess of said machine reel.
18. A magnetic tape unit according to claim 15, further comprising:
a machine reel having a recess for receiving said leader block; and
means for detecting slight movement of said arm corresponding to said play between said transmission gear and said arm by a tape tension applied to said magnetic tape at a tape end in rewinding said magnetic tape from said machine reel to thereby recognize said tape end, and then driving said threader motor to start said unthread operation of said tape threader.
19. A magnetic tape unit having a magnetic head for reading and writing data from and onto a magnetic tape, comprising:
a unit frame;
a flexible printed circuit board having an FPC connector, said FPC connector being fixed to said unit frame from an outside thereof; and
a printed circuit board having a board connector corresponding to said FPC connector;
said board connector of said printed circuit board being connected to said FPC connector by mounting said printed circuit board to said unit frame from the outside thereof.
20. A magnetic tape unit according to claim 19, further comprising an FPC holder for fixing said FPC connector to said unit frame so as to permit movement of said FPC connector in a direction perpendicular to a mounting direction of said printed circuit board to said unit frame.
21. A magnetic tape unit having a magnetic head for reading and writing data from and onto a magnetic tape, comprising:
a body having a display portion for displaying an operational condition of said magnetic tape unit and an operating portion for instructing an operation of said magnetic tape unit;
a decorative panel mounted so as to cover a front side of said body, said decorative panel having a first opening for exposing said display portion, a second opening for exposing said operating portion, and a third opening for allowing insertion of a magnetic tape cartridge; and
a metal plate provided inside said decorative panel, said metal plate having fourth to sixth openings respectively corresponding to said first to third openings of said decorative panel.
22. A magnetic tape unit according to claim 21, further comprising a metal subplate provided inside said metal plate.
23. A magnetic tape unit comprising:
a magnetic head for reading and writing data from and onto a magnetic tape;
driving means for traveling said magnetic tape kept in contact with said magnetic head during a readwrite operation of said magnetic head;
means for performing a reciprocating motion of said magnetic tape by a small distance with a predetermined period during a rest period where the readwrite operation of said magnetic head is not performed; and
housing for containing said magnetic head and said driving means, said housing being not provided with an air pump for creating an air gap between the magnetic tape and said magnetic head.
24. A magnetic tape unit comprising:
a magnetic head for reading and writing data from and onto a magnetic tape;
driving means for traveling said magnetic tape kept in contact with said magnetic head during a readwrite operation of said magnetic head;
means for performing a reciprocating motion of said magnetic tape by a small distance with a predetermined period during a rest period where the readwrite operation of said magnetic head is not performed; and
means for positioning said magnetic tape in contact with said magnetic head even during said rest period.