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900 Hz Soft-CarrierWhat is the 900 Hz soft carrier and how is it used in leased line modems? Soft-carrier allows the output transmission signal to softly go from a mark frequency of 1200 Hz, or a space frequency of 2200 Hz, to a zero frequency, or no signal. Rather than turn the carrier frequency off immediately, the modem will transmit a 900Hz signal to 'Unkey' the receiving modem. Once unkeyed the receiving modem will not try to interpret any further data on the line. This prevents the receiving equipment from generating false data signals at the end of a transmission. The Jumper settings and a sample diagram are shown below. 900 Hz Soft-Carrier On Time Switch Settings (SW3)You can set the 900 Hz soft-carrier on time from 1 millisecond (mS) to 15 milliseconds. shows the options for SW3 (positions 5-8), 900 Hz soft-carrier on time.
SW3 - 900 Hz Soft Carrier On Time Options, in this configuration, a 1ms Soft carrier on time would be used 900 Hz Soft-Carrier Enable / Disable Jumper (JP9) The 900 Hz soft-carrier enabled is the factory default setting. To enable 900 Hz soft-carrier, place jumpers across pins 3, 5 and 4, 6 of JP9. To disable the 900 Hz soft-carrier, place the jumpers across JP9, pins 1, 3 and 2, 4, as shown below. JP9 - 900 Hz Soft-Carrier 900 Hz Removed When CD Detected (JP6) If JP9 has been jumpered to enable the 900 Hz soft-carrier, then use JP6 to remove the 900 Hz when carrier detect (CD) is present. The default setting (no jumper), as shown in Figure 9, causes the 900 Hz soft-carrier to stay on for the duration of the timed program (SW3 settings above), and does not prematurely turn it off when carrier detect is present. Below shows examples of the timed program with the jumper installed, and with the jumper not installed.
JP6 - 900 Hz Removed When CD Detected
900 Hz Timed Program (JP6 and SW3) You may contact us in Campbell, CA by phone at 408-364-0500, fax to 408-364-0550, or via email at products@ase-systems.com. Normal business hours are 9:00AM to 6:00PM Pacific Time, M - F. Applied Systems Engineering, Inc. Copyright ©2003-2004 Applied Systems Engineering, Inc. |
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