Multitech MULTI MODEM II MT5600BA - Manual (Page 97)

C Loopback Tests
91
MultiModemII User Guide
3. Following the instructions in Chapter 7, set both modems to two-wire leased-
line mode. One should be set as the originate modem and the other as the an-
swer modem, but it does not matter which is which.
4. Turn on both units and wait for carrier detect (CD).
5. On the modem under test, short pins 2 and 3 of the RS-232C connector with a
paper clip or other metal device.
6. Enter data from your keyboard. Typing multiple uppercase U characters is a
good way to send an alternating test pattern of binary ones and zeroes. Data re-
ceived by the remote modem enters its analog receiver, is converted to digital
data, is reconverted into analog, and then is transmitted back to your modem.
Your modem passes this test if the data received on your monitor is the same as
the data entered from your keyboard.
7. To exit the test, turn off the modems.
Jumper pins 2 and 3.
VOLUME
EIA RS232C LEASED LINE PHONE
POWER
VOLUME
EIA RS232C LEASED LINE PHONE
POWER
Modem
under test
Local
modem
Figure C-5. Back-to-back test connections.