RFL Electronics RFL 9300 - Modem Connections

RFL 9300 RFL Electronics Inc.
October 20, 2004 5-10 (973) 334-3100
5.6 MODEM CONNECTIONS
The following paragraphs provide information for making connections to the RFL 9300's modem. Additional in-
formation can be found in Section 24, and in Appendix A at the back of this manual.
5.6.1 OUTPUT LEVEL CONTROL
There is a 21-turn potentiometer on the front of the RFL 93B MO Modem Module. This allows the transmit level
to be adjusted. The transmitter output will be about +8 dBm when the potentiometer is fully clockwise, and
about –20 dBm when it is fully counterclockwise.
5.6.2 MODEM I/O CONNECTIONS
Connections are made to the RFL 93B MO Modem Module through the 93 LC I/O Line Coupling Input/Output
Module, which is directly behind the RFL 93B MO module. Shielded twisted pairs should be used when making
connections between the 93 LC I/O and the telephone line.
Although the transformers in the RFL 93 LC I/O module are rated for 3750 Vac of isolation, the shields of the
twisted pairs should be connected to the ground stud on the back of the RFL 9300 as shown in Figure 5-3. At
the phone line junction box, the shields should be connected to the ground bus. This will provide an equipment
ground as well as capacitive shielding.
If there is a significant ground potential difference between the RFL 9300 and the phone line junction box, high
currents may flow through the shields. This could cause thermal damage to the cables. To prevent damage, a
heavy copper connection should be made in parallel with the shields to carry the current.
5.6.3 PHONE LINE COMMUNICATIONS
If you are using a Type 3002 unconditioned leased line for communications between RFL 9300 units, ask your
local telephone company for a SPOA line (Service Performance Objective Class A). This will guarantee com-
munications before, during, and after a fault condition. Your local telephone company should be able to provide
more information on telephone lines and SPOA line protection, or you can contact the factory. For more infor-
mation on SPOA Class A, see Appendix B.