GXW 4104 Firmware 1.0.1.10 should have hook-flash relay enabled. I've paired the device with a SPA3102, trying with both RFC2833 (AVT) and INFO application/hook-flash, but it's not working. Release note said it was (finally) implemented. Maybe a problem with application type?  Was anyone able to make hook-relay working?  Any suggestion will be welcome! From DEBUG Syslog i see  (.188=SPA, .185=GXW)INFO event:Oct 28 10:20:43 172.20.76.188 INFO sip:228@172.20.76.185:5060 SIP/2.0 Via: SIP/2.0/UDP 172.20.76.188:5060;branch=z9hG4bK-56296a11 From: 228 <sip:228@172.20.76.185>;tag=b57ee97d35c8d2a8o0 To: <sip:222228@172.20.76.185:5060>;tag=1725c71381f39541 Call-ID: c0862de1-d1d1b994@172.20.76.188 CSeq: 102 INFO Max-Forwards: 70 User-Agent: Linksys/SPA3102-5.1.7(GW) Content-Length: 11 Content-Type: application/hook-flash  Signal=hf Oct 28 10:20:43 172.20.76.188  Oct 28 10:20:43 172.20.76.188  Oct 28 10:20:43 172.20.76.185 GS_LOG: [00:0B:82:0C:DD:84][000][FF50][1.0.1.10] 374 sip_message.c Unknown SIP Content-Type: 0Oct 28 10:20:43 172.20.76.185 GS_LOG: [00:0B:82:0C:DD:84][000][FF50][1.0.1.10] 1610 sip.c Acc:0 Received SIP message: INFO sip:228@172.20.76.185:5060 SIP/2.0  Via: SIP/2.0/UDP 172.20.76.188:5060;branch=z9hG4bK-56296a11  From: 228 <sip:228@172.20.76.185>;tag=b57ee97d35c8d2a8o0  To: <sip:222228@172.20.76.185:5060>;tag=1725c71381f39541  Call-ID: c0862de1-d1d1b994@172.20.76.188  CSeq: 102 INFO  Max-Forwards: 70  User-Agent: Linksys/SPA3102-5.1.7(GW)  Content-Length: 11  Content-Type: application/hook-flash    Signal=hf  Oct 28 10:20:43 172.20.76.185 GS_LOG: [00:0B:82:0C:DD:84][000][FF50][1.0.1.10] 728 sip.c Sess: 0 Send SIP message: 200 To 172.20.76.188:5060Oct 28 10:20:43 172.20.76.185 GS_LOG: [00:0B:82:0C:DD:84][000][FF50][1.0.1.10] 900 sip.c Sess: 0 SIP/2.0 200 OK  Via: SIP/2.0/UDP 172.20.76.188:5060;branch=z9hG4bK-56296a11  From: 228 <sip:228@172.20.76.185>;tag=b57ee97d35c8d2a8o0  To: <sip:222228@172.20.76.185:5060>;tag=1725c71381f39541  Call-ID: c0862de1-d1d1b994@172.20.76.188  CSeq: 102 INFO  User-Agent: Grandstream GXW4104 (HW 1.0, Ch:0) 1.0.1.10  Supported: replaces, timer, 100rel, path  Content-Length: 0 AVT eventOct 31 11:20:27 172.20.76.183 ucDtmfTxMode: 1Oct 31 11:20:27 172.20.76.183 AVT Tx 16 startOct 31 11:20:27 172.20.76.183 AVT Tx 16 endOct 31 11:20:29 172.20.76.183 [0]Hook Flash(no reply from GXW)