I have a TEL-14 that was connected to the phone company and it worked just fine.
The station changed over to SIP and we connect our phone lines to a Cisco VG310 that was to provide the diletone. Well the call would come in and then hang up in 2 sec. We set vg310(config-voiceport)#loop-length long and that fixed the problem. By default the Cisco VG310 is set to loop short.
Instructions this is for a VG350 but is the same for the VG310 and 320
Loop-length configuration
The following configuration shows the use of the loop-length command:
vg350#config t
Enter configuration commands, one per line. End with CNTL/Z.
vg350(config)#voice-port 2/0/0
vg350(config-voiceport)#loop-length ?
long long loop length
short short loop length
vg350(config-voiceport)#loop-length long
vg350(config-voiceport)#shut
vg350(config-voiceport)#no shut
vg350(config-voiceport)#
*Mar 21 21:19:17.790: %LINK-3-UPDOWN: Interface Foreign Exchange Station 2/0/0, changed state to Administrative Shutdown
*Mar 21 21:19:19.094: %LINK-3-UPDOWN: Interface Foreign Exchange Station 2/0/0, changed state to up
vg350(config-voiceport)#
default to loop-length short.