incorporates a POINTER and LED to indicate synchronising condition. If
the generator- (II) frequency is higher or lower than that of mains- (I)
the pointer rotates in clockwise or anti-clockwise direction respectively.
The speed and direction of rotation depends upon difference in frequencies,
which guides the operator to speed-up or slow-down the generator. Synchronising
condition is determined by dark lamp method, wherein the pointer coincides
with synchronising mark and the LED does not glow. The LED glows in accordance
with difference in phase, frequency and amplitude of voltages. When the
pointer is towards the bright LED, it indicates the antiphase condition.