|P.O. ENGINEERING DEPT.
Issue 2, 13.9.50
ELECTRICAL CLOCKS - IMPULSE TYPE
Clock No. 38
Clock No. 38 is of the Veeder type and is provided at certain exchanges for
the timing of trunk calls and at exchanges where there are chargeable time
clocks for checking the accuracy of Clock No. 46. It is similar in appearance to a subscriber's meter and is fitted on the position keyshelf. The clock is driven by an impulse every six seconds
(Clock No. 36). The connexions are shown in Diagram AT 1871.
The impulse energizes the electromagnet M, which attracts the armature A. A pawl P, attached to the armature, revolves the
numeral disk W one tenth of a revolution for each impulse. The pawl P1 prevents backlash. The numeral disks W2, W3, and W4 are so arranged that one revolution of
W1 causes W2 to be advanced one step, one revolution of W2 causes W3 to be advanced one step, and half a revolution of W3 causes W4 to be advanced one step.
To reduce the operating noise, the back stop S is fitted with a rubber sleeve and the armature stroke stop C is covered with a buffer. The electromagnet has a resistance of 500 ohms and requires a minimum operating current of 30mA.