Outgoing spool failed

Elastix 2.2 Asterisk 1.8.Поток Е1. Стоит обзвонка на колл-файлах. В логах вот такое

    [May 19 08:01:01] VERBOSE[5623] pbx_spool.c:     -- Attempting call on DAHDI/g1/1111111111 for s@auto_dial_out_say_summa_do_20:1 (Retry 1)
[May 19 08:01:01] NOTICE[5623] channel.c: Unable to request channel DAHDI/g1/0565892141
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Executing [failed@auto_dial_out_say_summa_do_20:1] Set("OutgoingSpoolFailed", "tel=11111111") in new stack
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Executing [failed@auto_dial_out_say_summa_do_20:2] Set("OutgoingSpoolFailed", "hangUpState=2") in new stack
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Auto fallthrough, channel 'OutgoingSpoolFailed' status is 'UNKNOWN'
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Executing [h@auto_dial_out_say_summa_do_20:1] Goto("OutgoingSpoolFailed", "finally-2,1") in new stack
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Goto (auto_dial_out_say_summa_do_20,finally-2,1)
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Executing [finally-2@auto_dial_out_say_summa_do_20:1] MYSQL("OutgoingSpoolFailed", "Connect connid localhost user Password
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Executing [finally-2@auto_dial_out_say_summa_do_20:2] MYSQL("OutgoingSpoolFailed", "Query resultid 1 UPDATE dial_jobs SET
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Executing [finally-2@auto_dial_out_say_summa_do_20:3] MYSQL("OutgoingSpoolFailed", "Disconnect 1") in new stack
    [May 19 08:01:01] VERBOSE[5623] pbx.c:     -- Executing [finally-2@auto_dial_out_say_summa_do_20:4] Hangup("OutgoingSpoolFailed", "") in new stack
    [May 19 08:01:01] VERBOSE[5623] pbx.c:   == Spawn extension (auto_dial_out_say_summa_do_20, finally-2, 4) exited non-zero on 'OutgoingSpoolFailed'
    [May 19 08:01:01] NOTICE[5623] pbx_spool.c: Call failed to go through, reason (8) Congestion (circuits busy)
    [May 19 08:01:01] NOTICE[5623] pbx_spool.c: Queued call to DAHDI/g1/111111111 expired without completion after 0 attempts

Обзвонка классическая: считаем кол-во файлов и добавляем до максимального числа. Добавляем перемещением из темповой директории. Что означает Congestion (circuits busy) и "OutgoingSpoolFailed"?