U1911 AT0 trunk is always busy without any call

1.capture the U911 call log. display as below:

It seems that some anonymours call is always coming.

Line 285: [94][0x00000022][2016-01-31 12:10:03.78][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { BUSY------>IDLE }

Line 305: [94][0x00000023][2016-01-31 12:10:04.26][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { IDLE------>BUSY }

Line 1131: [94][0x00000023][2016-01-31 12:10:31.71][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { BUSY------>IDLE }

Line 1212: [94][0x00000024][2016-01-31 12:10:32.44][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { IDLE------>BUSY }

Line 2155: [94][0x00000024][2016-01-31 12:10:59.97][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { BUSY------>IDLE }

Line 2175: [94][0x00000025][2016-01-31 12:11:00.46][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { IDLE------>BUSY }

Line 3064: [94][0x00000025][2016-01-31 12:11:27.70][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { BUSY------>IDLE }

Line 3084: [94][0x00000026][2016-01-31 12:11:28.18][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { IDLE------>BUSY }

it is seems that manys anonymous call coming from PSTN.

2.directly connect a analog phone to PSTN, testing call is ok.  this means without PBX, the calling is ok with AT0 trunk.

3.show board, show board slot 1

4.depend on AT0 calling principle, to ensure that ringing current signals sent from FXS ports in an upper-level office can be detected, you must ensure that the ringing current detection range of FXO ports in the local office contains the corresponding ringing current voltage value.

   now there is no calling from PSTN, but the AT0 trunk is still busy, the PBX detect the ringing current voltage by mistake, actually some signal sent to PBX from PSTN is not ringing current signal, but PBX consider it as ringing current signal. so we try to adjust the value higher:

then test call ok.

ringing current detection threshold 1.capture the U911 call log. display as below:

It seems that some anonymours call is always coming.

Line 285: [94][0x00000022][2016-01-31 12:10:03.78][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { BUSY------>IDLE }

Line 305: [94][0x00000023][2016-01-31 12:10:04.26][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { IDLE------>BUSY }

Line 1131: [94][0x00000023][2016-01-31 12:10:31.71][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { BUSY------>IDLE }

Line 1212: [94][0x00000024][2016-01-31 12:10:32.44][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { IDLE------>BUSY }

Line 2155: [94][0x00000024][2016-01-31 12:10:59.97][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { BUSY------>IDLE }

Line 2175: [94][0x00000025][2016-01-31 12:11:00.46][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { IDLE------>BUSY }

Line 3064: [94][0x00000025][2016-01-31 12:11:27.70][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { BUSY------>IDLE }

Line 3084: [94][0x00000026][2016-01-31 12:11:28.18][At0.c 7430]dwTsn=[ 256] AT0_SetCircuitState { IDLE------>BUSY }

it is seems that manys anonymous call coming from PSTN.

2.directly connect a analog phone to PSTN, testing call is ok.  this means without PBX, the calling is ok with AT0 trunk.

3.show board, show board slot 1

4.depend on AT0 calling principle, to ensure that ringing current signals sent from FXS ports in an upper-level office can be detected, you must ensure that the ringing current detection range of FXO ports in the local office contains the corresponding ringing current voltage value.

   now there is no calling from PSTN, but the AT0 trunk is still busy, the PBX detect the ringing current voltage by mistake, actually some signal sent to PBX from PSTN is not ringing current signal, but PBX consider it as ringing current signal. so we try to adjust the ringing current detection threshold higher:

then test call ok.

when there is no calling from PSTN, but the AT0 trunk is still busy, the PBX detect the ringing current voltage by mistake, actually some signal sent to PBX from PSTN is not ringing current signal, but PBX consider it as ringing current signal. so we try to adjust the ringing current detection threshold higher.