1. A frequency divider comprising:
a function selector unit selecting a signal so that the selected signal in one of two feedback paths is dominantly input to a buffer unit, in synchronism with a clock signal frequency of which satisfies a certain condition;
the buffer unit buffering the signal input from the function selector unit and outputting the buffered signal;
the two feedback paths feeding back the output signal of the buffer unit to an input of the buffer unit; and
an inverter unit provided in one of the two feedback paths and inverting a signal value.
2. The frequency divider according to claim 1, wherein
the function selector comprises:
a first switch unit provided in one of the two feedback paths and turning on and off in synchronous with the clock signal in order to open and close one of the two feedback paths; and
a second switch unit provided in the other of the two feedback paths and turning on and off in an opposite timing to the first switch unit in order to open and close the other of the two feedback paths.
3. The frequency divider according to claim 1, wherein the function selector comprises:
a switch unit turning on and off in synchronous with the clock signal, wherein one of the two feedback paths is opened and closed by the switch unit while another of the two feedback paths including the inverter unit is always closed.
4. The frequency divider according to claim 2, wherein the first switch unit and the second switch unit transistor.
5. The frequency divider according to claim 1, wherein an operational delay of the inverter unit is adjustable.
6. The frequency divider according to claim 5, wherein the inverter unit comprises a variable resistor and the operational delay of the inverter unit is adjusted by changing the resistance of the variable resistor.
7. The frequency divider according to claim 1, further comprising:
a control unit turning off the inverter unit when the frequency divider is in a stand by mode.
8. The frequency divider according to claim 1, wherein
the certain condition is expressed by
1{2*(t_inv+t\u2014sw+t_buf)}<the frequency of the clock signal<min{1{2*(t\u2014sw+t_buf)},1(t_inv+t\u2014sw+t_buf)},
where t_inv is a delay time of the inverter unit, t_sw is a delay time of the function selector unit, t_buf is a delay time of the buffer unit and min{A, B} means smaller one of A and B.
9. A multiplexing system using the frequency divider according to claim 1.
10. A phase locked loop system using the frequency divider according to claim 1.
11. A clock generator using the frequency divider according to claim 1.
12. The frequency divider according to claim 3, wherein the switch unit is a transistor.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A multi-purpose head covering comprising:
a hat capable of covering at least a portion of a wearer’s head;
a mask capable of covering at least a portion of a wearer’s face, wherein the mask comprises a central body and two extensions, wherein the two extensions are disposed on either side of the central body and wherein each extension comprises a mask attachment member for attachment to the hat; and
a plurality of releasable fasteners attached to the mask, wherein fastening the releasable fasteners to one another changes the size of the mask.
2. The head covering of claim 1, wherein the two extensions are diametrically opposed to one another.
3. The head covering of claim 1, wherein the releasable fasteners are chosen from the group consisting of snaps, buttons, zippers, and hook and loop fasteners.
4. The head covering of claim 1, wherein the hat comprises a plurality of hat attachment members, wherein the hat attachment members are capable of releasably engaging the mask attachment members.
5. The head covering of claim 4, wherein the hat attachment members and the mask attachment members are chosen from a group consisting of snaps, buttons, zippers, and hook and loop fasteners.
6. The head covering of claim 1, the mask further comprising an upper surface and a lower surface, wherein the upper surface comprises elastic.
7. The head covering of claim 6, wherein the lower surface comprises elastic.
8. The head covering of claim 1, and further comprising a storage means that comprises a pocket within the hat, wherein the pocket is capable of being releasably fastened in a sealed configuration.
9. The head covering of claim 1, wherein the hat comprises a crown portion that is capable of covering at least a portion of the wearer’s head, wherein the crown portion comprises a sizing means for adjusting the size of the crown.
10. The head covering of claim 9, wherein the sizing means comprises an elastic cord that is sized to wrap at least partially around the crown portion and a spring driven locking member.
11. A multi-purpose head covering comprising:
a hat capable of covering at least a portion of a wearer’s head;
a mask capable of covering at least a portion of a wearer’s face, wherein the mask comprises a central body and two extensions, wherein the two extensions are disposed on either side of the central body and diametrically opposed to one another, wherein each extension comprises a mask attachment member for attachment to the hat; and
a plurality of releasable fasteners attached to the mask and approximately symmetrically arrayed with respect to a vertical line bisecting the mask into two approximately identical sides, wherein fastening a releasable fastener on one side to a matching releasable fastener on the other side changes the size of the mask.
12. The head covering of claim 11, wherein the two extensions are diametrically opposed to one another.
13. The head covering of claim 11, wherein the releasable fasteners are chosen from the group consisting of snaps, buttons, zippers, and hook and loop fasteners.
14. The head covering of claim 11, wherein the hat comprises a plurality of hat attachment members, wherein the hat attachment members are capable of releasably engaging the mask attachment members.
15. The head covering of claim 14, wherein the hat attachment members and the mask attachment members are chosen from a group consisting of snaps, buttons, zippers, and hook and loop fasteners.
16. The head covering of claim 11, the mask further comprising an upper surface and a lower surface, wherein the upper surface comprises elastic.
17. The head covering of claim 16, wherein the lower surface comprises elastic.
18. The head covering of claim 11, and further comprising a storage means that comprises a pocket within the hat, wherein the pocket is capable of being releasably fastened in a sealed configuration.
19. The head covering of claim 11, wherein the hat comprises a crown portion that is capable of covering at least a portion of the wearer’s head, wherein the crown portion comprises a sizing means for adjusting the size of the crown.
20. The head covering of claim 19, wherein the sizing means comprises an elastic cord that is sized to wrap at least partially around the crown portion and a spring driven locking member.