| 摘要 |
<p>PURPOSE:To switch a main power source to an incorporated battery instantaneously by using a semiconductor electronic circuit and to secure the normal operation of a radio telephone set even in power source switching during telephone service and transmission and reception of a signal. CONSTITUTION:A partial voltage EM of the main power source is supplied to the negative terminal of a voltage comparator U1 and a reference voltage EZ2 is supplied to the positive terminal; when EM>EZ2, the switch transistor (TR) Q2 of the incorporated battery 19 is turned off and the output voltage of a voltage comparator U2 rises to EZ1 to operate a switch TRQ1, thus outputting the main source voltage to a load. Then, when the main source voltage drops until EM< EZ2, the output voltage of the comparator U1 rises to EZ1 to operate the TRQ2, which supplies the electric power of the battery 19 to the load while the TRQ1 is turned off. Said switching operations are carried out at the same time and the radio telephone set in use is operated normally.</p> |
