| 摘要 |
PCT No. PCT/SE83/00195 Sec. 371 Date Jan. 13, 1984 Sec. 102(e) Date Jan. 13, 1984 PCT Filed May 17, 1983 PCT Pub. No. WO83/04355 PCT Pub. Date Dec. 8, 1983.The invention relates to a method and apparatus in duplex transmission of digital information between subscribers connected to terminals associated with each other in a telecommunication network of the time multiplex type in which information is transmitted in the form of binary words in specially assigned time slots, of carrying out with the aid of parity check, during traffic in progress, through-connection testing for checking that a correct connection has been set up after a switching path has been established. The through-connection check is started and detected in the same station (terminal). After detected correct parity, which is done with the aid of a parity check means (M1) and a comparison circuit (OR), there is generated a parity bit with intentional incorrect polarity for sending on the line towards the next station. Generation of desired parity is done with the aid of an apparatus including a local processor (MP), a control memory (CM), a counter (TR) and said comparison circuit. All stations along a switching path are of equal value and contain the same means. A central processor assigns one of the stations (TCT), at the setting up of a connection, to be the control station for the through-connection test. The control bit with intentionally incorrect parity is switched straight through remaining switching points and is looped in the line terminal (PCM2) where information from-the B subscriber is received. The loop connection is carried out with the aid of a parity check circuit (M2) for extracting the parity bit from the terminal side, and a further parity check circuit (M3) for the loop formation itself and feeding out the parity bit back towards the TCT station. A check is made in the latter that it is the intentionally erroneous parity bit which is detected, and if this is the case the correct parity is sent, subsequent to which it is awaited that the correct parity will traverse the switching path and once again be detected in the TCT station. After this detection, a signal is sent to the central processor that the through-connection test is completed, after which this control is broken off and normal parity monitoring takes over, the latter not being embraced by the invention, however. |
