thanks for your reply,
sorry,but it was a bit late,i've misled you.
as you said,the output should be high with the receiver pulses triggering it
but when i simulated a receiver failure by removing the wire feeding the pulses
from the receiver ,the output remained high. i had a resistor 100k from trigger
pin down to zero volts so surely the output should have dropped?
i need that drop to enable a second receiver to take over should the first one fail.i've never used the 4047 before, i chose it because it's retriggerable
and i think if the receiver output 'jammed' in the high position it would still time out or am i wrong on that one?
the timing period of 2.5 seconds was to try the chip out so my meter could follow it . about 50 milliseconds would be needed in actual use.
maybe i should try another chip?