intermetently no dial tone!

Hi
i have a cordless binatone md 750 phone. Every 2/3 weeks we find there is no dial tone and when we switch the power off and on then the dial tone returns and all is normal until it happens again!!am not sure if the fault is with the phone or this happens after some mobile or land line numbers have rung my numbers! thanking in advance for advise/help.
ih

1st suspect and port of call would be the battery in the handset is on its way out........

thanks johnboy42 the battery were replaced few months ago and am sure are in sound condition and the battery meter is always nearly full.
ih