A device, comprising: a transmitter, and a detection portion having a plate shape and including a first set of one or more indication sensors, which, in operation, detects one or more indications input by a user; the device being characterized in that the device is configured to be attachable and detachable to and from both of a protective cover and a piece of electronic equipment, wherein the piece of electronic equipment has a plate shape, a back and a front, the front including a display with a second set of one or more indication sensors, wherein the device further comprises a securing portion extending from the detection portion and configured to secure the device to the piece of electronic equipment, wherein the securing portion is sized and shaped to fit between the back of the piece of electronic equipment and a base part of the protective cover to secure the device to the piece of electronic equipment, wherein the transmitter, in operation, transmits signals to the piece of electronic equipment based on the indications input by the user and detected by the first set of one or more indication sensors, wherein the securing portion is secured between the back of the piece of electronic equipment and the base part of the protective cover by friction, wherein the securing portion has a rectangular shape with a side joined to a side surface of the detection portion, wherein a first part of the securing portion has a triangular shape with a base joined to the side surface of the detection portion and a friction coefficient higher than a friction coefficient of a second part of the securing portion, or the securing portion has a triangular shape with a base region joined to a side surface of the detection portion, wherein the securing portion has a friction coefficient in a vertex region which is lower than a friction coefficient of the base region. a transmitter, and a detection portion having a plate shape and including a first set of one or more indication sensors, which, in operation, detects one or more indications input by a user; the device being characterized in that the device is configured to be attachable and detachable to and from both of a protective cover and a piece of electronic equipment, wherein the piece of electronic equipment has a plate shape, a back and a front, the front including a display with a second set of one or more indication sensors, wherein the device further comprises a securing portion extending from the detection portion and configured to secure the device to the piece of electronic equipment, wherein the securing portion is sized and shaped to fit between the back of the piece of electronic equipment and a base part of the protective cover to secure the device to the piece of electronic equipment, wherein the transmitter, in operation, transmits signals to the piece of electronic equipment based on the indications input by the user and detected by the first set of one or more indication sensors, wherein the securing portion is secured between the back of the piece of electronic equipment and the base part of the protective cover by friction, wherein the securing portion has a rectangular shape with a side joined to a side surface of the detection portion, wherein a first part of the securing portion has a triangular shape with a base joined to the side surface of the detection portion and a friction coefficient higher than a friction coefficient of a second part of the securing portion, or the securing portion has a triangular shape with a base region joined to a side surface of the detection portion, wherein the securing portion has a friction coefficient in a vertex region which is lower than a friction coefficient of the base region.