376227
This causes blocked calls or dropped call s. However , it can also apply to landline phones , in which not enough trunking telephone circuit s are available into and out of any given telephone exchange or equivalent switching office at any level of the public switched telephone network ( PSTN ) .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 None