| 摘要 |
PURPOSE:To simplify a circuit constitution, to make miniaturization and to decrease the number of externally mounted components by using the main body circuit section of transmission/reception oscillation circuit in common and switching a constant circuit added to the main body circuit in setting the oscillating frequency. CONSTITUTION:A capacitor 24 and a resistor 26 are used for a time constant circuit for reception frequency decision and the capacitor 24 and resistors 30A, 30B are used for a time constant circuit for deciding a transmission frequency. A switch 28 is switched to the position of a transmission side (a) or a reception side (b) in response to L/H of the level of a signal A fed to a terminal 34. Further, a switch 32 is switched to the position c1 or c2 in response to H/L level of the switching signal B. Thus, in the reception mode the capacitor 24 and the resistor 26 are added to the oscillation main body circuit 22 and in the transmission mode, the connection of the resistor 26 is cut off and the resistors 30A, 30B are connected to the main body circuit 22. When the switch 32 is switched alternately by H/L, the transmission frequency fT1 is set by the capacitor 24 and the resistor 30A and the fT2 is set by the capacitor 24 and the resistor 30B. |
