23 Feb Among those electromechanical automatic switches, strowger’s step by step switching system was the most pupular and widely used and even. Strowger developed a system of automatic switching using an electromechanicalcal switch based around around electromagnets and pawls. With the help of his. 3 Oct Strowger wasn’t the first to come up with the idea of an automatic telephone switching system, but his concept was the first that would work on.

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The below figure shows how a rotary dial looks like. The above photo is of a working Strowger exchange; it was working until July at a public building in Catford and then replaced by strowger switching system modern exchange. Two-motion selectors typically have 10 rows of 10 outlets, thus possible outlets altogether.

Strowger he produced strowger switching system working model in US Patent No. The reasons for survival of this system even in some strowger switching system of the world are its a high system availability b comprehensibility and c cheapness and simplicity.

Figure 3b – A “Group” Selector and a ‘bank’ for it to slot into. This strowger switching system is used to indicate that a number is out of service, faulty or that a spare line has been dialled. Get My Free Ebook. As systeem previously, manual switching required an operator for every call and thus was expensive on manpower, however, when first developed, automatic switching systems were comparitively expensive systrm in the Post-war period onwards female labour was cheap, so the advanages of moving to an automatic system were not great.

This signal has different patterns in different systems. AE ; the two companies merged in The Strowger switch is strwoger first commercially successful electromechanical stepping switch telephone exchange system.

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Strowger switch

This page was last edited on systwm Augustat The stepping motion is controlled by the current pulses coming from the originating customer’s telegraph keys, and later from the rotary dial. Among those electromechanical automatic switches, strowger’s step by step switching system was the most pupular and widely used and even now in some part of the world, it is in strowger switching system.


Harris strowger switching system Moses A.

Group selectors take only ONE digit from the caller, and step up the number of levels according to the digit dialled. The following figure will help you understand the internal mechanism.

The central office switching equipment has a two-motion stepping switch. The shape of the Impulsing cam is such that the break and make periods are in the ratio of 2: In this system, a moving wiper strowger switching system contacts strowger switching system the end moved upto and around a bank of many other contacts, making a connection with any one of them. The telegraph keys or telephone dial creates trains of on-off current pulses corresponding to the digitsand 0 which sends 10 pulses.

The Strowger switch uses two telegraph-type keys on a telephone set for dialing. Selectors previous to the Final Selectors are different; they are called Group Strowger switching system.

Now, drawing the fingerplate round in the clockwise direction to the finger stop position and letting the dial free by withdrawing the finger, makes a number dialed. Whenever a caller asked to be put through to Strowger, calls were deliberately put through to his strowger switching system. The Strowger Switching system is also called the step-by-step switching system as the connections are established in a step-by-step manner.

In the rest of the picture you can see the racks of selectors. An interlock ensures that the spring on the shaft rotates it to angular home position before it drops to its home position by gravity.

Previous systems had all been designed for a fixed number of subscribers to be switched directly to each other in a mesh arrangement. The ring generator was entirely electromechanical; different cadences and tones were produced by rotating cams connected to a generator. This article strowger switching system additional citations for verification. When the dial returns, the pawl engages and rotates the ratchet.

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Strowger switch – Wikipedia

In strowger switching system late ‘s Almon B. The pulse dialing technique is where there is making and breaking of the strowger switching system loops. In order to ensure that successive digits didn’t come too soon and thus be mistaken for pulses belonging to the previous digit, the finger stop on the dial was put some way round so that after removing your finger from the dial, there was a minimum time taken for the dial to return to the home position.

This mechanism should be switchign in the telephone set, in order to connect the call automatically to the required subscriber. Meyer, strowger formed his company “Strowger Automatic Telephone Exchange” in october Of them, the Pulse dialing is the most commonly used form of dialing till date. This will lead to the dialing of a wrong number. With the help of his nephew Walter S. The cam mechanism or trigger mechanism syrowger in dialing.

The ratchet, gear wheel, strowger switching system wheel and the governor are all stationary during the clockwise movement of the dial. Strowger switching system set has a finger plate the arrangement of which makes the dialing time appropriate.

Strowger Switch: the 19th-century design invention that flipped the phone industry on its head

Most numbers dialled are several strowger switching system longer, and therefore pass through a chain of selectors. The privacy of the calls and the details of the called and the calling subscribers are at stake. The commercial version of the Strowger switch, as developed by the Strowger Automatic Telephone Exchange Company, used strowger switching system rotary dial for signalling to the exchange.

This might disturb and affect the performance of speaker, microphone and bell contained in the telephone.