Please select the most similar patent number from A, B, C and D. Which number is?
An operating key-free pulse oximeter based on Photoelectric effect is provided. The pulse oximeter comprises an optical frequency converter, a luminous driving circuit, a display, a microprocessor, a voltage stabilizing circuit module, a light coupled device and a power supply. The light coupled device connects with the voltage stabilizing circuit module, the voltage stabilizing circuit module connects with the microprocessor and the optical frequency converter, the microprocessor also connects with the optical frequency converter, the luminous driving circuit and the display. In which, after the distance between the light coupled device and the obstruction reaches a certain distance D, the light coupled device is in on-state or off-state, thus the startup or shutdown operation of the Operating key-free pulse oximeter is implemented. The pulse oximeter is operated without key, and is easy to operate.
A: A backlight drive circuit, comprising: a voltage-stabilizing circuit for receiving and filtering input voltage, and outputting voltage-stabilized direct current (VCC); a booster circuit connected with the voltage-stabilizing circuit, and used for receiving and boosting the voltage-stabilized direct current (VCC) and then outputting the boosted direct current to a light emitting diode (LED) light bar; a control circuit connected with the booster circuit, and used for providing a pulse-width modulation (PWM) square wave and controlling the booster circuit to supply power for the LED light bar. The booster circuit comprises an MOS transistor or a triode; at least three resistors having similar or same resistance value(s) are connected in parallel between the ground and the source electrode of the MOS transistor or the collector of the triode. Correspondingly, also provided is a liquid crystal display employing the backlight drive circuit. The drive circuit improves the precision of the current outputted to an LED light bar.
B: Provided are a latch and a D trigger. The latch comprises: a switch, a variable resistance-type memory, a voltage-dividing circuit and a voltage converter. When the switch is in a turned on state, the voltage converter is used for outputting an output signal of the latch according to an input signal of the latch, the output signal remaining consistent with the input signal. When the switch changes from the turned on state to a turned off state, the variable resistance-type memory is used for coordinating with the voltage-dividing circuit to enable the output signal of the latch when the switch is in the turned off state to remain consistent with the output signal of the latch when the switch is in the turned on state, thereby implementing a non-volatile latching function. Since the latch in the present invention uses relatively few components, circuit structure in simple, circuit area is reduced, and the level of integration of existing logic circuits can be improved.
C: An activation system for an electric meter and an electronic device, the system comprising: a controllable circuit (1) that is disposed between a power supply source and an electric meter, wherein one terminal of the controllable circuit (1) is connected to the power supply source, and another terminal of the controllable circuit (1) is connected to the electric meter, and a control terminal of the controllable circuit (1) is connected to a microprocessor; the controllable circuit (1) is used to be turned on by an activation signal sent by the microprocessor so as to activate the electric meter, and the activation signal is sent when the microprocessor detects that the electric meter needs to be activated. The foregoing system may conveniently and promptly achieve the automatic activation of the electric meter without manual operation by a user, and the circuit is simple. Some conventional components may be used, which may effectively save costs.
D: An oximeter (1), comprising: a blood oxygen collecting unit (2), which is provided with a first light-emitting unit (21), a second light-emitting unit (22), and a light-receiving sensor (23), the first light-emitting unit (21) emitting a red light, the second light-emitting unit (22) emitting an infrared light, and the light-receiving sensor (23) receiving the red light emitted by the first light-emitting unit (21) and not absorbed by the human body and the infrared light emitted by the second light-emitting unit (22) and not absorbed by the human body and converting the lights into an electric signal; a storage unit (3), which stores a first threshold; a microprocessor (4), which calculates the blood oxygen saturation of the human body on the basis of the electric signal detected by the light-receiving sensor (23) and comprises a determining unit (41), the determining unit (41) determining whether the blood oxygen saturation is less than the first threshold; and a display unit (5), which flash displays the blood oxygen saturation at a first frequency in a case where the determining unit (41) determines that the blood oxygen saturation is less than the first threshold.
Answer: D