D8SSW-E

SR250-D8bu-SSW

Impulser for unipolair slave clocks with a change-over contact

IBM, Simplex, International Time Recording and older Z+M slave clocks are mostly supplied with a change-over contact. The function of the contact is to synchronize hourly a slave clock, going fast or slow, to the master again.

Via a two- or three wire cable the clocks are connected to a suitable master clock.

With a two wire connection, diode D is essential. During an impulse the current flows from a to c. Moving to the 59th minute position the contact changes over and following impulses will be sperred by the diode. Now the master clock gives 15 impulses in sequence which is mostly enough to pick up a slow going movement. Because the current only flows via the diode and switch from c to a, the next minute-impulse is in reverse polairity. The movement(s) will follow again to the 60th minute.


	Because switching back of the contact does not take place in the same minute position of every movement, the master clock (SR250) will give up to 10 minute-impulses of reverse polairity. After that the current is flowing, up to the 59th minute-impulse, from a to c again.


			With a three wire connection up to the 59th minute position the impulse current flows from a naar to c. After that up to 10 minute-impulses from a and b to c. Reverse polairity is not necessary.

		The SR250-D8bu-SSW (D, NL, B), M8bu-SSW (GB) or W8bu-SSW (US) is adjustable to both wire connections and can not be used for other systems.




			IBM slave movement Contact change-over by a cam on the upper gear-wheel.



	ITR slave movement Contact change-over by the cam on the upper part.



			Z+M slave movement Contact change-over by a cam under the upper gear-wheel.