Back to back connection

Hello,

As an initial scenario I’m following this example:

http://www.voip.unam.mx/mediawiki/index.php/Instalación_y_Configuración_de_la_Tarjeta_TE110P

My understanding is that this scenario should allow the establishment of call from A to B and vice-versa. But when I test it I find that communications works in only one way.

Maybe the problem is with signaling and the CPE NEt configuration but Iwould like to know
if it is possible to connect two asterisk using an E1 link and to have bidirectional calls.

Best regards,

Bruno