Strowger Switching System

Strowger Switching System is the first automatic telephone exchange .The Strowger switch is the first commercially successful electromechanical stepping switch telephone exchange system. It was developed by the Strowger Automatic Telephone Exchange Company founded in 1891 by Almon Brown Strowger. Because of its operational characteristics it is also known as a step-by-step (SXS) switch.

1. STROWGER SWITCHING SYSTEM G OURAB C HANDRA G HOSH S URENDRA I NSTITUTE OF E NGINEERING & M ANAGEMENT

2. CONTENTS Introduction Advantages of automated switching Rotary dial telephone Configuration of a step by step switching system Line finders Selector hunters Strowger switching components DESIGN PARAMETERS Disadvantage Reference

3. INTRODUCTION The first automated switching system. Inventor: Almon Brown Strowger . Year: 12 th March 1889.

4. ADVANTAGES Language independent. Greater degree of privacy is obtained. Fast establishment and release of calls .

5. ROTARY DIAL TELEPHONE A train of pulses is used to represent a digit in the subscriber number. Successive digits are distinguished by a inter-digit gap.

6. CONFIGURATION OF A STEP BY STEP SWITCHING SYSTEM

7. LINE FINDERS It searches and finds the line of a subscriber to be connected to the first selector associated with it.

8. SELECTOR HUNTERS It searches and seizes a selector from the switching matrix part.

9. STROWGER SWITCHING COMPONENTS Uni -selector. Two Motion Selectors.

10. Uni -selector

11. Two Motion Selectors

12. HOW TWO MOTION SELECTOR WORKS Dialed No. is ‘ 5789 ‘

13. WHEN 5 IS DIALED

14. WHEN 7 IS DIALED

15. WHEN 8 IS DIALED

16. WHEN 9 IS DIALED

17. DESIGN PARAMETERS Number of subscriber lines, N Total number of switching elements, S Cost of the switching system, C C=S X Cs + Cc + Cch Cs – cost per switching element Cc – cost of the common control subsystem Cch – cost of the common hardware Switching capacity, SC

18. DESIGN PARAMETERS Traffic handling capacity, TC=2(SC)/N Equipment utilization factor, EUF EUF=(number of SE in operation) / (total number of SE) SE stands for Switching Element Number of switching stages, K Average switching time per stage, Tst Call setup time, Ts= KTst + T0 Cost capacity index , CCI= SC / (C/N)

19. DISADVANTAGES High maintenance cost. Big amount of man power is required. Premium quality material is required .

20. REFERENCE Telecommunication Systems by, T.Vishwanathan Hicken-65 (You tube channel). Prof. S.Mandal (for guidance).

21. QUESTION & ANSWER SESSION

22. THANK YOU