zone-centrehttp://www.oed.com/dictionary/zone-centre_n-a%3Ftab%3Dmeaning_and_usezone centre | zone center, n.
First published 1986; not fully revised

zone centre | zone centernoun

spec. in Telephony.
  1. 1934–
    An exchange which acts as a main switching centre in an area containing a number of exchange groups.
    1. 1934
      Level 94..is used for trunk calls instead of level o in the case of exchanges in Trunk Zone Centres.
      G. S. Berkeley, Traffic & Trunking Principles in Automatic Telephony i. 12
    2. 1948
      The group centre extends the call to the zone centre where it is routed to the distant zone centre exchange.
      J. Atkinson, Herbert & Procter's Telephony vol. I. xii. 234/2
    3. 1960
      A suitable exchange (zone centre) is established within each zone to handle the long-distance calls to and from that zone.
      R. Syski, Introduction to Congestion Theory in Telephone Systems ii. 53
    4. 1971
      Zone centre, exchange acting as the main switching centre.
      Glossary Electrotechnical, Power Terms (British Standards Institution) iii. ii. 8

Originally published as part of the entry for zone, n.

zone, n. was first published in 1921; not fully revised.