Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2000-05-26
2003-04-29
Ullah, Akm E. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S139000
Reexamination Certificate
active
06554490
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic apparatus and, more specifically, to an electronic apparatus having a function of communication using a fiber optic cable or an electric cable, which uses a detachable communication cable.
2. Description of the Background Art
Among digital video camera (digital VTRs with camera; digital video camera, hereinafter referred to as DVC) recording motion pictures, some have a function of transferring digital data at high speed to other electronic apparatuses, by connecting electronic apparatuses with each other by a cable, utilizing a standard such as IEEE1394.
In most cases, such electronic apparatuses are used as portable apparatuses. Therefore, generally, such an apparatus is used for recording pictures or the like while it is not connected to a cable, and communication with other apparatus is established by connecting a cable when communication becomes necessary.
An electric cable having a 4-pin or 6-pin terminal has been standardized as a communication medium in accordance with IEEE1394. As to the optical fiber, a standard specifying use of two optical fibers has been proposed. Further, mainly for portable apparatuses, study has been made for transferring signals in accordance with IEEE1394 standard over one optical fiber.
According to IEEE1394, when an electronic apparatus has a plurality of ports, it is necessary for the electronic apparatus to function as a repeater to relay a signal from one electronic apparatus to another electronic apparatus. Therefore, power supply to a physical layer circuit is adapted to be supplied constantly.
In an electronic apparatus not mainly used for communication, constant power supply to the physical layer circuit when the cable is not connected is unnecessary. Though IEEE1394 suggests possibility of considerable reduction of power consumption of a communication circuit when the communication cable is not connected, specific method thereof is not specified in the standard.
Further, a receptacle specified in IEEE1394 does not have any mechanism for detecting whether a plug is inserted to/removed from the receptacle. Therefore, it is necessary to detect voltage levels of signal lines in accordance with IEEE1394, to obtain information of connection between the plug and the receptacle from the result of analysis. This means that power must be supplied constantly to the communication circuit to keep the circuit in operation.
Here is the problem that even when the apparatus is fully disconnected from a communication circuit and the communication circuit is not in use, power consumption by the communication circuit portion cannot be made zero. In a portable apparatus such as a DVC, the communication circuit portion operates not only at the time of communication but also at the time of recording, for example, and hence power is consumed at the communication circuit portion which is essentially not in use. In such portable apparatus which are in most cases battery-operated, this leads to shorter discharge life of the battery, and the recordable time in recording operation is undesirably made shorter.
Generally, not only in DVCs but also in battery operated portable apparatuses, wasteful power consumption at the communication circuit portion not at the time of communication shortens discharge time of the battery, making it difficult to ensure long operation time of the apparatuses.
Therefore, reduction in power consumption of the electronic apparatus is an important problem.
As one technique related to lower power consumption of an electronic apparatus, Japanese Patent Laying-Open No. 7-57819 discloses a technique in which power supply of the electronic apparatus as a whole is shut off, when a cable is not connected to the electronic apparatus.
Though it is possible to control power supply to the overall electronic apparatus by the technique described in Japanese Patent Laying-Open No. 7-57819, it is not possible to reduce power consumption by the communication circuit portion only of the electronic apparatus, or to control power on port by port basis in accordance with IEEE1394, for example.
Japanese Patent Laying-Open No. 10-70508 discloses another related technique providing both spatial optical communication function and optical communication function through fiber optic cable, in which driving power for optical communication is increased to perform spatial optical communication when a fiber optic cable is not connected, and driving power for optical communication is reduced to perform optical communication through an optical fiber when the fiber optic cable is connected.
The technique described in Japanese Patent Laying-Open No. 10-70508 is applicable when spatial optical communication and optical communication through fiber optic cable are switched. The technique, however, cannot directly be applied to a DVC, for example, of which communication with other apparatus is established only through a communication cable.
In addition to the problem of power consumption, there is another problem of stabilizing operation when electronic apparatuses in operation are to be connected with each other by a communication cable.
Generally, when electronic apparatuses in operation are to be connected to each other by a communication cable, it is not guaranteed that the ground (reference potential) of an apparatus is at the same potential as the ground of the other apparatus to be connected, immediately before connection. Accordingly, when signal electrodes of the apparatuses contact with each other before the ground electrodes are connected to each other, it is possible that signal electrodes of the two apparatuses may contact with excessive potential difference therebetween. Therefore, a receiving device or a transmitting device may possibly be damaged.
FIG. 10
shows shapes of a plug and a receptacle in compliance with IEEE13344 standard.
Referring to
FIG. 10
, a receptacle
410
includes a power supply related electrode
415
, and a signal electrode
417
. Power supply related electrode
415
is positioned close to a tip end portion of receptacle
410
, whereas signal electrode
417
is placed recessed therefrom. A plug
400
includes plug side electrodes
420
corresponding to respective electrodes of receptacle
410
.
Therefore, when plug
400
is connected to receptacle
410
, power supply related electrode
415
comes to be in contact with the corresponding plug side electrode
420
before signal electrode
417
comes into contact with the corresponding plug side electrode
420
. Therefore, between the apparatuses, the ground (reference potential) and the power supply are first connected, and after the apparatuses are ready to have the signal lines connected to each other, the signal related electrode
417
comes to be in contact with the plug side electrode
420
, establishing safe connection of the signal line. Accordingly, problems such as an unexpected application of excessive voltage to the receiving device or the transmitting device or malfunction caused by unexpected data input to a state transition circuit in accordance with IEEE1394 can be solved.
Generally, when electronic apparatuses in operation are to be connected with each other by a communication cable, unexpected data may possibly be input as a noise to the receiving side dependent on the order of connection of a plurality of signal lines, causing malfunction of a communication circuit.
In order to solve such a problem, a technique for preventing malfunction at the time of connection between the plug and the receptacle is described in Japanese Patent Laying-Open No. 2-53125.
FIG. 11
shows configurations of a plug and a receptor disclosed in Japanese Patent Laying-Open No. 2-53125.
Referring to
FIG. 11
, in a plug
500
and a receptacle
510
, electrodes are arranged aligned in the direction vertical to the direction of insertion. At opposing ends of the plug and the receptacle, electrodes
512
and
514
for detecting connection and corresponding plug side electrodes
502
and
504
are p
Ichikawa Yuji
Nagura Kazuhito
Nakano Daisuke
Nishimura Takashi
Sumi Kazuyuki
Conlin David G.
Connelly-Cushwa Michelle R.
Edwards & Angell LLP
Penny, V John J.
Sharp Kabushiki Kaisha
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