CTI Products RCD Standard - Remote Comparator Display - Manual (Page 108)

MCN Remote Comparator Display Appendix B
CTI Products, Inc. Modem Support
68-10856-210
102
10.1.4 Testing Local Back to Back Modems
It is a good idea to test your system locally before installing the HIB at a remote
location. Here are some hints to help you set up your test with the modems.
For dial-up modems, connect both modems to dial-up phone lines. In-house
analog extension lines on a PBX can be used.
Note: If you use a PBX extension line, be sure to use a standard analog extension
line, not a digital extension line.
If you are using dial-up modems, set them up using two telephone lines or
extensions. Program the PC modem to call from its phone to the other modem..
Leased line modems may have problems being hooked directly together without a
phone line. Without a phone line, the modem will see a very high receive signal
level. This can cause some modems to generate garbage data on the receive side.
Reducing the receive signal level to about -10 to -16 dBm will usually cure this
problem.
One way to reduce this level is by reducing the transmit level to -10 dBm on both
modems. You can do this by entering the Modem Configuration menu on the
V.3229 modem. If you do this, be sure to reset the levels when you install the
system!
Another way to avoid receive garbage due to high levels is to connect the modems
via an attenuator. A 12 dB attenuator for a 2-wire circuit can be made with 4
resistors as shown:
>-------- 560 Ohms--------<
| |
Modem 1 1 K 1 K Modem 2
| |
>-------- 560 Ohms--------<
Use two of these circuits for a 4-wire connection.
This appendix outlines the PC to modem and HIB to modem interfaces for the
MCN Remote Comparator Display systems. This information is provided as an
additional aid to help set up and maintain your PC comparator display system.
10.2 Modem Programming
The UDS V.3225 and 3229 modems are programmed with the front control panel.
See section 12 for details about these front panel controls.
Most other modems can only be programmed from their DTE port. Programming
involves disconnecting the modem from the HIB and connecting it to dumb
terminal or a PC running communication software such as Procomm™.