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Design Guide for Cisco Unity Release 5.x
OL-14619-01
Chapter 6 Integrating Cisco Unity with the Phone System
Integrating with Circuit-Switched Phone Systems by Using PIMG or TIMG Units
When older versions of Cisco Unity integrated with a circuit-switched phone system by using a serial
integration, if the phone system did not use standard serial packets (such as SMDI or MCI), it was
possible to adjust the serial packet definitions by using Cisco
Unity .avd files. Unfortunately,
PIMG/TIMG units do not allow customization of serial packet definitions, so only phone systems that
comply with the standards will work.
The serial port on PIMG unit was originally designed as a management port rather than as a standard
RS-232 serial port. Consequently, a custom serial cable (which is available from Cisco) is necessary for
the datalink between the phone system and the master PIMG unit. The pinout of the custom serial cable
is available in the PIMG Integration Guide at
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_installation_and_configuration_g
uides_list.html.
Increasing Port Capacity
PIMG units have eight ports. To increase system port capacity, multiple PIMG units can be stacked. For
example, if 32 ports are needed, 4 PIMG units can be stacked. When stacking two or more PIMG units,
each PIMG unit must communicate with Cisco
Unity by using a different IP port. The first PIMG talks
to Cisco
Unity port 5060, and each successive unit uses the next higher port (5061, 5062, and so on).
TIMG units, which integrate with circuit-switched phone systems that support T1-CAS, have 24 T1 ports
per span in a single rack-optimized unit. Single span and dual span TIMG units are available.
Cisco Unity Failover
PIMG/TIMG integrations support Cisco Unity failover. Configuration changes are required both for the
PIMG/TIMG units and for the Cisco
Unity servers, as described in the applicable integration guide. The
IP addresses of both Cisco
Unity servers must be entered in each PIMG/TIMG unit. The settings in
UTIM (Cisco
Unity Telephony Integration Manager) for the secondary Cisco Unity server must match
those of the primary Cisco
Unity server. This includes the integration number, which may vary.
Cisco Unity failover is different for PIMG/TIMG integrations in that a Cisco Unity server cannot
explicitly tell a PIMG unit whether it is active and should receive calls. Rather, PIMG/TIMG units will
infer the active server based upon which Cisco
Unity server responds to incoming calls and upon
keepalive messages received from the primary Cisco
Unity server. When the primary Cisco Unity server
is active, the PIMG/TIMG units will send calls to it. If the primary server does not answer or send
keepalive messages, the PIMG/TIMG units will pull the call back and send it to the secondary
Cisco
Unity server. When the secondary Cisco Unity server answers, the PIMG/TIMG units will assume
the secondary is the active server, and route all further calls to the secondary server. While the secondary
Cisco
Unity server is active, the PIMG/TIMG units will send periodic keepalive messages to the primary
server. When the primary Cisco
Unity server responds, the PIMG/TIMG units will route calls to the
primary server.