Abstract: A muldem (100) has a monitor (101) which automatically sequentially tests data paths through the muldem for detection of malfunctions in the muldem. Standby data path protective switching means (108, 109) provides alternate data paths through the muldem in the event of a malfunction. The monitor may be manually overridden and locked to a specified data path for continued analysis of such path. Additionally, a selected path may be manually locked out from switching to standby. The monitor automatically checks before switching any data path to standby, to prevent a selected path from being switched, while permitting automatic protective switching of the other data paths.

Abstract: A muldem (100) has a monitor (101) for testing data path failures through the muldem (100) by comparing the latter's input and output. The muldem (100) has normally on-line data paths (103, 104) therethrough, and includes normally off-line standby data protective switching means (108, 109) providing alternate data paths. The monitor (101) tests on-line and off-line data paths before and after protective switching to the standby alternate data path, to guard against silent failures and to prevent switching to an inoperative path. In an auto-revert mode, a latched display continues to display an alarm, after the malfunction is corrected and the muldem has switched from standby to main.

Abstract: A muldem (100) includes a transmit multiplexer section (103, 104) combining a variety of low speed and intermediate speed digital data inputs into a single high speed data output. A monitor (101) is provided for testing data path failures through the muldem (100) by comparing the latter's input and output. The monitor (101) includes comparing means (806, FIGS. 13a and b) which accepts both low and intermediate speed data from the inputs for comparison against the high speed data from the output.

Abstract: A muldem (100) includes a transmit multiplexer section (103, 104) combining a variety of low speed and intermediate speed data inputs into a single high speed data output and a demultiplexer section providing low and intermediate speed outputs from a high speed input. A monitor tests data paths of the muldem for detection of malfunctions and initiates protective switching through a standby alternate data path around the low or intermediate speed circuits and, independently, around the high speed circuits.

Abstract: A muldem (100) has a monitor (101) for testing data path failures and standby data protective switching means (108, 109) providing an alternate data path in the event of a malfunction. The system accepts up to fifty-six standard low speed T1 LS lines (1.544 Mb/s), up to fourteen standard intermediate speed T2 lines (6.312 Mb/s), or any combination of T1 and T2 lines to generate to standard HS lines (44.736 Mb/s). The T1 circuitry is replaceably interchangeable with the T2 circuitry.

Abstract: A muldem (100) has a monitor (101) for testing data path failures through the muldem (100) by comparing the latter's input and output. The monitor (101) tests itself by injecting errors into one of the compared data streams for detection thereof if the monitor (101) and comparing means (806, FIG. 13a and b) is operating properly. Error injection is particularly accomplished by an error generator (922, FIG. 14) synchronously clocked with a data stream (904) through an exclusive OR gate (938). The error generator (922) includes a free running gated oscillator (924) and a pair of ganged flip-flops (926, 928) toggled by a clock signal (936) recovered from the data stream (904).

Abstract: A muldem (100) has a monitor (101) for testing data path failures through the muldem (100) by comparing the latter's input and output. The monitor (101) includes comparing means (806, FIGS. 13a and b) with a data comparator (880, FIGS. 13b and 17) for bit error detection by comparision of a pair of data streams (A+B) processed through the monitor (101) from the input and output of the muldem (100). The data comparator (880) delays one of the data streams (A) by a fixed amount and variably delays the other data stream (B), and then slipshifts the data streams in time until they are in alignment to be compared. The data comparator (880) detects noncoincidences of bits in the two data streams and counts such errors over a given sampling interval, providing a bit error rate. If this rate is above a user selectable threshold, then a malfunction in the tested data path is probable, so the path is retested, using a longer sampling interval, to improve the statistical accuracy of the test.

Abstract: A muldem (100) has a monitor (101) for testing data path failures and standby data protective switching means (108, 109) providing alternate standby data paths in the event of a malfunction. The system accepts a maximum of fifty-six standard low speed T1 lines (1.544 Mb/s), fourteen standard intermediate speedT2 lines (6.312 Mb/s), or any combination of T1 and T2 lines to generate two standard high speed T3 lines (44.736 Mb/s). The structure allows for partial equipping of low and intermediate speed circuits by accepting any number of circuits up to the maximum capacity of the high speed circuits. The system provides automated adjustment for expansion and contraction of the system while in operation. Individual T1 and T2 signal paths may be added or removed with no disturbance to any other path. The monitor automatically adjusts to test data paths through added T1 or T2 circuits and to ignore data paths through removed T1 or T2 circuits.