Patent GB-1497180-A (GB)
Title: Electronic timepieces
IPC: G04C9/08
Filed: 1975-11-27
Abstract: 1497180 Electronic timepieces DAINI SEIKOSHA KK 27 Nov 1975 [28 Nov 1974] 48857/75 Heading G3T In an electronic timepiece with a crystal controlled oscillator 11 Fig. 1 followed by a frequency divider 12, 13 having a 1 Hz output to control a time display including a seconds display, e.g. secs hand driven by a stepping motor, there is provided an arrangement for automatically correcting the seconds display following manual operation of a switch S at an exact minute time signal, e.g. at a radio broadcast pip. The display drive is automatically speeded up briefly when the seconds display is in retard and is automatically inhibited when the display is in advance. Normal rate is automatically resumed at an instant determined by the difference between secs display when the switch is operated and an exact minute. The term "in retard" is used if when the switch is closed the seconds hand indicates between 30 and 59 sees although the correct time is an exact minute. The term "in advance" is used when the seconds hand incorrectly indicates between 0 and 30 secs. Operation. A latching circuit 17 Fig. 1, stores binary data representing the second hand position and upon receipt of a clockpulse delivered by a circuit 23 when push switch S is closed, this data is transferred via a complement number generating circuit 18 to a latching circuit 19 which stores the complement numbers (i.e. the difference between a number of seconds and 30). The complement numbers appear at the Q outputs of 19 when a clockpulse is received from 23. After the contents of 17 are transferred to circuit 19 the circuit 23 sends a pulse to reset the Q outputs of 17 to zero; thereafter its content changes every second. Closure of switch S and the reset of circuit 17 also results in a pulse from an advance/retard control circuit 21, which causes a change in the output of drive signal generator 20 to 2 Hz and the stepping motor will rotate at twice normal speed. Assuming a 15 second retard when S was depressed, then after 15 seconds the output of 17 will assume a binary state (17) as in the truth table Fig. 3 (not shown) i.e. 10001 - since a jump circuit 16 causes the latch circuit 17 to jump from state 15 to 17, whereupon a coincidence circuit 22, which compares the outputs of latching circuits 17 and 19, produces a pulse causing the driving signal generator 20 output to revert to the normal 1 Hz. Thus if the seconds hand is 15 seconds in retard and it is driven at twice normal speed it will be at position 12 corresponding to 12 o'clock on the dial Fig. 2a (not shown) in 7¢ seconds and in 15 seconds will be at positon 3 which is the correct position 15 seconds after the switch was closed at the radio broadcast pip. If the seconds hand is in advance by 15 seconds (i.e. in position 3 Fig. 2b not shown), the Q outputs of 17 will be 10001 and the Q output of control circuit 21 will be at low level. When switch S is closed the outputs of switching circuit 23 and the resulting low level output of control circuit 21 inhibit the driving signal from circuit 20 so that the stepping motor will stop. This state continues until the coincidence circuit 22 detects coincidence between the contents of 17 and 19 and produces a pulse whereupon the normal 1 Hz output of driving signal generator circuit 20 resumes with the second hand in the correct positon.