Nowadays more and more equipment rely on battery to get power energy .In the case of ATLAS 210 the HF preamplifier  and the microphone preamplifier  are independantly fed with a non rechargeable battery .In normal operation the energy consumption is quite low (few milliamp) and the life expectancy of the battery is high (up to 2 years) .Unfortunatly it is very easy to forget to shut down  the preamplifier when leaving the station .Obviously we can put a LED (Light Emmitting Diode) to indicate when the preamplifier is on and off , but the LED is also consumming quite a lot of current (few milli amp) and therefore  reducing the life time of the battery even when using  low power LED .One way  to increase this life time is to feed the low power LED not directly from the power supply  but through  a chopper .Here is the BATTERY SAVER . The battery saver is an astable oscillator using a CMOS integrated circuit (IC) . The LED is fed by the circuit .In the OFF position the consumption of the circuit is very low (in the 20 micro amp range) .On the ON position the consumption is adjusted by a resistor in series with the LED .With the to day technology it is very easy to buy LED giving a very decent brightness with  1 milli amp current .In order to reduce the average consumption the LED is fed during a very short period of time  thanks to the astable circuit .The circuit is a 4049 IC  (6 inverters in the package , only 2 of them are in fact used ) .The duration of the ON and OFF are adjusted with resistor R1 and R2 in conjunction with the capacitor C .The values are not critical and can be changed .In our case we chose C= 10 microfarad  with R1= 100 000 ohm and R2= 15 000 ohm .The blinking rate is in the 2 second range the duration of LED ON STATE being around 0.2 second .The circuit is working with power suppy ranging from 3 volt up to 13 volt .So as to reduce as low as possible the total consumption it is important to ground the unused inputs Full size schematic