
3. T-Line  and R-Line  are shorted or mixed up.
  | 
  | Shorted or mixed up  | |
(B)  | (A)  | ||
  | 
  | ||
  | EXCHANGE  | 
  | |
Symptom:  | A can not dial.  | 
  | |
  | 
  | ||
  | 
  | stations.  | 
  | 
  | When B dials A, noise will be heard at  | 
  | |
  | 
  | B immediately after the calling tone.  | 
  | 
4.
(B)  | (A)  | 
  | 
  | ||
  | EXCHANGE  | Conversed  | |
  | 
  | ||
Symptom:  | A can not dial.  | 
  | |
  | Conversation is impossible between  | ||
  | 
  | stations.  | 
  | 
  | When B dials A, noise will be heard at B.  | ||
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