I go through tutorial about USB modem and this is what I get:
MikroTik RouterOS 5.23 (c) 1999-2013 http://www.mikrotik.com/
[admin@MikroTik] > /system resource usb print
# DEVICE VENDOR NAME SPEED
0 1:1 RB400 EHCI 480 Mbps
1 1:5 HUAWEI Technology HUAWEI Mobile 480 Mbps
[admin@MikroTik] > /port print
Flags: I - inactive
# NAME CHANNELS USED-BY BAUD-RATE
0 usb1 4 9600
[admin@MikroTik] > /system serial-terminal usb1 channel=3
[Ctrl-A is the prefix key]
^RSSI:16
^BOOT:33388506,0,0,0,20
^RSSI:16
^RSSI:16
^RSSI:19
^RSSI:19
^RSSI:19
^RSSI:19
^RSSI:19
^RSSI:19
^BOOT:33388506,0,0,0,20