Exchange Halted by ‘Circuit Breaker’

A plunge in stock-index futures prices this morning on the Chicago Mercantile Exchange triggered a two-minute trading halt that is one of the “circuit breakers” intended to prevent a runaway stock-market collapse.

All Standard & Poor’s 500 stock-index futures contracts fell the permitted opening limit of 5 points in the first 10 minutes, forcing exchange officials to declare a trading halt from 9:40 a.m. to 9:42 a.m., according to an exchange spokesman. He said prices continued to fall when trading resumed. The near-month contract, for September delivery, came within 1/10th point of a 12-point loss, which is the next circuit-breaker limit, before prices rallied.