TELEPHONE RELAYS U AND Y TYPE (PART 1 and 2)

e [Music] yeah I know so relays can't talk but if we could you'd hear quite a story there are more than 150 million of us in the Bell System yes there are about 70,000 reays for each 10,000 lines of crossbar equipment the equipment in this office cost over a million dollar and about a third of it is for relays this marker circuit has almost a thousand relays and there are several of these circuits in this office but relays are in a lot of other places too they're in switchboards they're in dial private branch ex changes they're in 1 a key equipment before this lady completes her call about a thousand relays will swing into action relays are important all right without them the fast accurate telephone service we have today would be impossible it's an interesting story how relay is developed how they are made how they work and how we should handle them so they'll keep on doing a good job we relays are proud of our family tree yes it's a long history of growth to meet the demands of a fast growing telephone industry here's the great great grandfather of them all born before the year 1900 he was the first relay used widely in telephone systems and all telephone relays are his descendants you'll find most of the old relay types in the Bell Laboratories Museum in New York City here are some of the early types great great grandfather is at the left some of these relays still are used in many of our offices today the 122 type is used in manual exchanges the 221 type is used in step-by-step dial Central offices and here's the 114 type used as a tripping relay in both panel and crossbar offices in the early 1900s the Bell Laboratories developed what is commonly called the flat type relay to make mass production possible they are designated by letter here are an A and A B relay here's an R relay here are the parts of a flat type relay without the Springs notice how few parts there are it's much simpler than the round type on the left this made mass production possible but the telephone business never stand still relay operation had to be more critical and exacting so in 1935 the Bell Laboratories develop the U and Y type relays like this little fellow they have a lot of advantages here they are they look like twins and yet their duties are quite different the Bell Laboratories working with Western Electric designed them so that many similar parts tools and methods could be used to build them and when the design was completed Western Electric took over yes we took over but because we had worked with bell Laboratories it was easier to mod ify machines build others and work out mass production problems combining speed with care and precision here's where the relay starts in the peace parts shop the heart of the relay is the core the flat surfaces are cut with extreme accuracy armatures are Stamped Out by the thousands relay Springs are Stamped Out at 10,000 an hour Hing spring rivets are formed in the Armature core brackets are stamped and formed first the core is welded to the bracket then the weld is tested with a side pressure of 300 lb when the parts are ready for a kneeling they are placed in sealed pots to prevent oxidation then into the furnace here is where the relay obtains the required magnetic characteristics it's not an ordinary furnace the temperature and cooling rate are carefully control but there's still more to be done before the Armature is ready for assembly the U type armatures are provided with two non-magnetic stop discs now in this modern electroplating tank the armatures are chromium plated under the most exacting controls a disc of nickel silver is welded on to reduce wear on the spring stud where it rests against the Armature hinge springs are attached to the Armature by a Pneumatic Riveter this spring was not used on the early U and Y type relays meanwhile other parts have been manufactured contacts of precious metal are welded onto Springs spot checks to destruction assure quality spring studs are assembled studs are carefully checked for length spring insulators are baked for at least 20 2 3 hours then stored in sealed cabinets and kept dry with a drying agent once taken to the assembly line these insulators must be used within 4 hours or rebaked in the coil winding Department standard uniform coils are wound eight at a time a sheet of acetate is automatically placed between each layer of of the winding the number of turns is accurately indicated on a mechanical counter now the coils are cut apart an ingenious machine completely automatic seals flares and corrugates both ends of the coil with heat and pressure at the same time it sizes the center hole so it will slip readily over the core and makes each coil of uniform length now the winding leads are positioned and the spool heads and coil are assembled in one quick operation the leads are soldered in place with great care the leads are slack so vibrations during the service life of the relay will not break them and now in order to pass its final test the coil is checked automatically for resistance direction of winding and voltage breakdown on the final assembly line all the separate parts are brought together Nimble fingers build the required pileups in special jigs at the end of the conveyor an operator compresses each pileup under a pressure of 2,000 lb high tensil steel screws are driven home with a Pneumatic screwdriver in which the torque is carefully control and now the relays are mounted on a temporary plate and adjusted and inspected to meet exacting requirements another relay ready to do its part in the big job of giving service it's one of millions but each getting individual attention the best materials Precision manufacture and assembly and rigid tests but wait that's not all right over at the Bell Laboratories an engineer is going to show us how U and Y type relays are better than the other flat type relays first of all let's compare the magnetic circuits of the U and R relays here is the r relay this is the magnetic circuit the lines of force must follow to operate the Armature any Gap or constriction in their path has the same effect on the magnetic circuit as resistance in an electrical circuit only in the magnetic circuit it's called reluctance thus this air gap and these thin hinges tend to limit the lines of force and consequently the pull exerted on the relay Armature in the u relay and also in the Y relay a major change in design permits the Armature to overlap the end yolk this large metal to metal contact reduces the reluctance thus increasing the magnetic force so you see with very little increase in the size of the relay or amount of electrical energy in the coil the UR Relay can operate as many as 12 contact Springs in each pileup compared to only six Springs in each pileup for the rtype relay another very important Improvement introduced in the U and Y relays was the bifurcated or twin contact spring this greatly reduces circuit troubles or if a speck of dust or lint prevents one contact from making the current path through the other contact usually remains undisturbed without this Improvement the crossbar Circuit of today might be impracticable and yet the twin contact is not the whole answer look at the dust and lint on these contacts this can happen in the central office when the covers are left off it's what we call man-made trouble don't belittle the value of central office cleanliness and dust protection relay covers should be removed only when absolutely necessary and replaced as soon as possible before we leave the bated spring let's talk about contact alignment this is the ideal alignment of a pair of standard or light contacts these contacts are misaligned but it is permissible since the width of each contact lies wholly within the length of its mating bar this of course is not satisfactory because it reduces the contact area and thereby the life of the contact yes the UR relay is much improved over the r type we can actually see this Improvement by means of high-speed photography perhaps you'd like to see how pictures are taken of operations that are too fast to see with the naked eye this fast tax camera developed right here in the Laboratories and made by Western Electric can slow down action more than 200 times 100 ft of film run through the camera in less than a second they're just about ready to start ready start that's it and that picture will take 3 minutes to show at normal speed and now I know you'll want to see some of the pictures we've made first I'd like to show you with this projector an everyday incident familiar to all of us drops of milk falling into a cup of coffee now here it is is seen Through The Eyes of a Fast Tax camera it gives a pretty good idea of how high-speed photography slows down motion so we can see things that we never knew took place now let's look at a u relay that is properly adjusted first we'll examine the Armature bounce with the help of high-speed photography we'll do this twice so the first time watch the Armature the Armature operates now we'll release the relay see it bounce against the adjusting nut now this time watch The Springs see them vibrate this spring vibration is always present but it will not cause trouble if the relay is properly adjusted if you look closely you will see that there is no false contact operation it's the result of changes in Armature design and careful proportioning of the stationary and movable Springs this Improvement was necessary to meet the more exacting requirements of the newer switching systems high-speed photography the oscillograph oscilloscope and a number of precise measuring devices make it possible for us to develop equipment that will meet the requirements of telephone service today requirements for adjusting relays properly are right here in the Bell System practices they are developed to secure good performance with the least headaches for the maintenance man yes no question about it you relays are accurate and reliable you're ready to do a good job if you'll do what the man said adjust us properly when we're in trouble how about that Jack that's right occasionally a real fails unless we follow the adjustment procedures and the Bell System practices the value of careful relay design and manufacturer can be lost but of course the Bell laboratory's Engineers are always looking for improvements here at the Bell Labs they've got almost 4,000 relays in this test setup working day and night to find out how to cut down trouble and make them last longer in another room they're running tests on Dust exclusion this relay is being given a pull test test to find out what affects its ability to operate a spring load yes reays are reliable and wellb built and so long as they keep on working leave them alone because tinkering can cause a lot of relay trouble actually only a small percentage of the relays in an office ever develop trouble and have to be readjusted but when they do need adjusting remember do the job right according to the book how about it it will keep me out of trouble and make your job a lot easier too [Music] [Applause]