(a(i))[1]
length variations.
(a(ii))[1]
pressure changes.
(b)[4]
A relay may be used as the output stage of a sensing circuit. The output of one particular sensing circuit is either $+2\,\text{V}$ or $-2\,\text{V}$. On Fig. 10.1, draw symbols for a relay and any other required component so that the external circuit is switched on only when the output from the sensing circuit is $+2\,\text{V}$.