Multi-Tech Systems BL-Series manual 4A. Back-to-Back Test Cabling

MultiModemBL User Guide

8.5Back-to-Back Test

This test lets you connect two MultiModems with an RJ-11 cable to verify proper operation. Using a modem that is known to be operational, you can test a second modem that is suspect.

1.Plug the modular ends of an RJ-11 cable into both MultiModem’s LEASE jack connectors.

2.Force DTR ON in both local and remote modems (Switch #1 DOWN).

3.Enter the command AT$SB9600$BA0&W0<CR> on both local and remote modems. This sets the serial speed to 9600bps. Make sure that the terminal/computer is set for 9600 bps.

4.Set both modems in Leased-Line mode (DIP-Switch # 10 DOWN).

5.Set one modem to Answer enabled (DIP-Switch #5 UP) and the other modem to Originate enabled (DIP-Switch #5 DOWN). Note it does not matter which modem (local/remote) is set to Answer/Originate—just so they are set opposite.

6.Set DIP-Switch # 3 UP on both local and remote modems. This changes the transmit level to -15dB and this change is necessary to operate in back-to-back mode

7.Turn on both units and wait for carrier detect (CD).

8.Short out pins 2 and 3 on the RS-232C interface on the remote modem (i.e.., with a paper clip or some other metal device).

Remote Site: Short Pins #2 and

#3 on the RS-232 Interface

PHONE	PSTN	LEASE	EIA RS232C
			ON
			OFF
			VOLUME
			POWER

PHONE	PSTN	LEASE	EIA RS232C
			ON
			OFF
			VOLUME
			POWER

Figure 8-4A. Back-to-Back Test Cabling

9. Entered characters should echo back to the sending modem.

Back-to-Back

Cable

Local	Remote Modem
Modem	in Loopback Mode

Figure 8-4B. Back-to-Back Testing

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