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Major types of telephone exchanges

Short answer

A telephone exchange is a switching centre that connects, supervises and releases temporary paths between subscribers. Major types: manual (magneto or central battery), Strowger, crossbar, electronic SPC (space or time division), and by role local, tandem, toll, international gateway and PBX.

What is telephone exchange? Describe the major types of telephone exchanges in brief.

Telephone exchange

A telephone exchange is the switching centre where subscriber lines and trunks end, and where a temporary path is set up between a calling and a called subscriber on demand, supervised and then released. It removes the need for direct lines between every pair of users.

Major types

  1. Manual exchange – an operator connects calls with cords and jacks.
    • Local battery (magneto): each telephone has its own battery; caller turns a magneto to signal.
    • Central battery (CB): battery at the exchange; lifting the handset lights a lamp at the switchboard.
  2. Strowger (step-by-step) exchange – electromechanical; two-motion selectors step directly with dial pulses (direct control).
  3. Crossbar exchange – electromechanical crossbar switches with common control (registers, markers); faster and more reliable than Strowger.
  4. Electronic (SPC) exchange – a stored-program computer controls the switching network; offers many services.
    • Space-division – separate metallic/reed-relay path for each call.
    • Time-division (digital) – PCM speech switched in time slots (e.g. E10, EWSD, 5ESS, AXE); used in modern networks.
  5. Exchanges by network role: local (end) exchange, tandem exchange, toll/trunk exchange, international gateway, and private branch exchange (PBX/PABX) in offices.

✓ Answer checked by Claude Opus 5.5 (high effort)

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