Smartjack

Smartjack is a smart and intelligent device placed right between telephone company's demarcation and customer premises. We usually call this kind of device NID but smartjack is different since it has a smart function to test a connectivity check.

Smartjack's loopback
Smartjacks also typically provide diagnostic capabilities. A very common capability provided by a smartjack is loopback, such that the signal from the telephone company is transmitted back to the telephone company. This allows the telephone company to test the line from the central office, without the need to have test equipment at the customer site.

If you are unable to perform the hard and soft loopback tests or if the hard and soft loopback tests reveal that that the Cisco gateway and the cable run (to the telco demarc) are working correctly, telco-assisted loopback might be an option.


 * 1) Ask the telco to provide loopbacks towards your premises from the telco switches. Monitor the looped circuit from the router. In this scenario, test the circuit as an ISDN interface.
 * 2) Contact your telco, and ask them to perform a loopback test to the SmartJack. The telco can test the line from the central office  and does not need to have test equipment at your site. Usually, the telco can activate the loopback remotely and does not need to have personnel at your site. When looped back, your equipment is disconnected from the line.

Links

 * T1/E1 Loopback Testing and Troubleshooting - http://www.cisco.com/c/en/us/support/docs/voice/device-signaling/116492-trouble-t1e1-00.html