Verbosity is at least 5
    -- Remote UNIX connection
voice*CLI> bri debug span 2
Enabled debugging on span 2
2 < Protocol Discriminator: Q.931 (8)  len=20
2 < Call Ref: len= 1 (reference 1/0x1) (Originator)
2 < Message type: SETUP (5)
2 < [2 042  032  802  902  a32 ]
2 < Bearer Capability (len= 5) [ Ext: 1  Q.931 Std: 0  Info transfer capability: Speech (0)
2 <                              Ext: 1  Trans mode/rate: 64kbps, circuit-mode (16)
2 <                              Ext: 1  User information layer 1: A-Law (35)
2 < [2 6c2  052  002  802  322  372  322 ]
2 < Calling Number (len= 7) [ Ext: 0  TON: Unknown Number Type (0)  NPI: Unknown Number Plan (0)
2 <                           Presentation: Presentation permitted, user number not screened (0) '272' ]
2 < [2 7d2  022  912  812 ]
2 < High-layer compatibilty (len= 4) [ 2 0x91 2 0x81 2  ]
2 -- Making new call for cr 1
2 -- Processing Q.931 Call Setup
2 -- Processing IE 4 (cs0, Bearer Capability)
2 -- Processing IE 108 (cs0, Calling Party Number)
2 -- Processing IE 125 (cs0, High-layer Compatibility)
2 > Protocol Discriminator: Q.931 (8)  len=11
2 > Call Ref: len= 1 (reference 129/0x81) (Terminator)
2 > Message type: SETUP ACKNOWLEDGE (13)
2 > [2 182  012  892 ]
2 > Channel ID (len= 3) [ Ext: 1  IntID: Implicit, Other Spare: 0, Exclusive Dchan: 0
2 >                        ChanSel: B1 channel
2                          ]
2 > [2 1e2  022  812  822 ]
2 > Progress Indicator (len= 4) [ Ext: 1  Coding: CCITT (ITU) standard (0) 0: 0   Location: Private network serving the local user (1)
2 >                               Ext: 1  Progress Description: Called equipment is non-ISDN. (2) ]
    -- Accepting overlap voice call from '272' to '<unspecified>' on channel 0/1, span 2
    -- Starting simple switch on 'Zap/4-1'
    -- Going to extension s|1 because of empty extension received on overlap call