| 摘要 |
PURPOSE:To operate effectively, make the device compact and lower the cost by using the digital electronic counter easy to be integrated circuit in detecting the modulated frequency of the control signal. CONSTITUTION:The rectifying output voltage level of the control signal b is discriminated by the comparison switching circuit 21 to obtain the change-over signal (m). The detecting output (c) of the amplitude detector 4 is directly or through the limitter 22 fed to the counter 23 and the count result thereof is discriminated by the discriminator 24 in accordance with the change-over signal (n) for discriminating if it is 982.5Hz or not. These two change-over switches (m), (n) are fed to the change-over circuit 13 to operate the desired control signal discrimnating operation and when the control signal does not reach a predetermined level, it is enforcibly made monoral operation. |
