ISDN – BRI (Basic Rate Interface)
https://www.cisco.com/c/en/us/td/docs/ios/dial/configuration/guide/12_2sr/dia_12_2sr_book/dia_cfg_isdn_bri.html https://www.cisco.com/c/en/us/support/docs/dial-access/integrated-services-digital-networks-isdn-channel-associated-signaling-cas/22802-bri-loopback-call.html https://www.cisco.com/c/en/us/support/docs/voice/digital-ccs/15415-bri-voice-port-cfg.html Telstra Exit Date...