| 摘要 |
<p>Digital data transmission lines are tested by a relatively small addition to the circuitry in repeater stations. At each end of each repeater a short circuit (SS1,SS2) can be applied across the send and transmit lines. For this purpose each repeater has two identical regulator units (Reg1,Reg2). Each has receive (EAZ1,EAZ2) and output amplifier (V1,V2) sections. Connected to each receive section is a command pulse evaluator (KE1,KE2) whose output is connected to a conditional counter (ZZ1,ZZ2) and also, to pass on a command, to the output amplifier. The inputs to the conditional counters are interconnected. The counter (ZZ1,ZZ2) output orders the condition of the repeater, and can order closure of the short circuiting switch. It is arranged that a short circuit command is only acted upon the second time that the command is received. The correctly timed arrival of a command from the opposite direction can suppress action. By these means a specific repeater on the system can be selected to apply the short circuit whilst keeping all repeaters identical.</p> |
