Hardware manual

Issue 8 Electra Elite
5 - 66 Installing Electronic Telephone Units
4.12.6 Connectors
The PRT(1)-U( )ETU has two connectors:
CN1 Connects to the backboard
CN3 9-pin RS-232C connector used for
maintenance
4.12.7 Connections
Figure 5-36 PRT(1)-U( ) ETU Connector
MDF
TA
TB
RA
RB
ISDN PRI
Provider
CSU
The CSU may not always be required.
ISDN PRI