Method and apparatus for testing a subscriber line group marker of a telephone central office cross bar switching device

Abstract

Disclosed is a method and apparatus adapted to be used in testing a subscriber line group marker, of a telephone central office switching device, wherein such markers are energizable by application of central office battery potential through a normally open path but closed in response to a subscriber's telephone going off hook and/or an incoming call from a distant office. Testing takes place without removing the marker physically from its central office switching environment by essentially eliminating any chance of it being electrically energizable by anyone but the testing party. Such is accomplished by placing the instant of time the marker is to be tested essentially under the sole control of the testing party by: (a) electrically obstructing said normally open path so that it remains open even when a subscriber goes off hook and/or notwithstanding the presence of an incoming call demanding service; (b) providing a normally open electrical path from the central office battery to the marker; and (c) at an instant of arbitrary choosing, closing the last mentioned electrical path and applying for predetermined period of time central office battery potential directly to the marker to energize it.

Dependencies are inferred from the claim text.