User`s manual

U.S. Robotics I-modem Command Reference
Testing • Page 14-9
Register S18, the I-modem automatically ends the test when the test timeout is reached.
When the test ends, the I-modem returns a three-digit code, followed by OK. A code of
000 indicates no errors were found; a code of 255 indicates 255 or more errors.
Data errors indicate a problem with the remote device or with the phone link.
6. Send AT&M4, unless you used a reset command (ATZ or ATZ!).
Testing the I-modem Using S16
Register S16 is a bit-mapped register. (See Chapter 1, Using the AT Command Set, for
instructions for setting bit-mapped registers.)
Note Earlier U.S. Robotics modems require bit 3 to be enabled to grant digital
loopback testing to a remote device. The I-modem requires its default &T4
Table 14Ð1. S-register 16
Bit Value Function
2 4 Remote digital loopback with built-in test pattern
3 8 Remote digital loopback using keyboard data