Showing papers on "Loopback published in 1979"

Method and apparatus for carrying out loopback test

Abstract: The present invention discloses a method for carrying out a loopback test in a data communication system having a first data communication station, a second data communication station and a transmission line connected therebetween. The first data communication station transmits a succession of a first pseudo-random noise signal, a loopback test signal and a second pseudo-random noise signal to the second data communication station by utilizing a usual information data channel, and requires no special channel for carrying out the loopback test. When the second data communication station detects the first pseudo-random noise signal, it transmits the loopback test signal to the first data communication station in order to check the coincidence of the transmitted and the received loopback test signals. The second pseudo-random noise signal denotes the end of the loopback test.

Testing system for data transmission paths

Abstract: A loopback testing system for an asynchronously operating fully duplex data transmission path comprising proximate and remote stations, a proximate-to-remote data transmission channel for transmitting data to the remote station at a relatively high maximum data transmission rate, and a remote-to-proximate data transmission channel for transmitting data to the proximate station at a relatively low maximum data transmission rate. A test-waveform generator applies to the proximate station, for transmission along the proximate-to-remote channel, a test waveform presenting a data transmission rate at least approximately equal to the aforementioned higher maximum data transmission rate. A loopback circuit at the remote station receives the thusly transmitted test waveform and reapplies it at the remote station for transmission back to the proximate station along the remote-to-proximate channel. However, the loopback circuit includes a digital frequency divider which reduces the waveform-element transmission rate presented by the test waveform to such a level that the waveform-element duration of the test waveform, as transmitted back to the proximate station, at least approximately corresponds to the aforementioned lower maximum data transmission rate.

Loop back system for duplex loop transmission system

Abstract: PURPOSE:To enable general loop back instruction, by interrupting to the station at the post stage, even at loop back, and giving the function releasing the loop back to the station through the normal reception of the signal in loop back from the station of the post stage. CONSTITUTION:When general loop back instruction is received from a transmission line 3 via a receiver 21a, a decoder 27c interprete it, and a switching control circuit 27a gives a switching signal 32a to switching circuits 26c and 26d so that a transmission/reception control circuit 24 is inserted between the output of the receiver 21a and the input of transmission 22a, 22b. Thus, the general loop back instruction is in loop back through the transmitter 22b of a station 2a and transmitted to the station at the post stage with the transmitter 22a.

Communication system by loop transmission system

Abstract: PURPOSE:To speed up the switching of loop at failure, by taking a state of loop back mode at an upper side from a failed point and taking a state of return mode from the lower side. CONSTITUTION:The frame information is circulated via a loop transmission path 3-0. Further, the clock detection circuits 16-0-16-3 for loop transmission units 2-0- 2-3 monitor the circulation of the frame information. Further, when a disconnection is caused, the circuits 16-3 and 16-0 switch the return switching section S1. Next, the maintenance control adaptor 4 of the unit 2-0 designates the unit 2-2 to output the loop back control instruction and switches the loop back switching section S2. Thus, the disconnected position is automatically avoided to form the loop using transmission lines 3-0 and 3-1.