Instruction manual

DS1 Facility Interface
The trunks terminating on a 4ESS switch must be administered as either tie or direct inward
dialing trunk types. The tie trunks can be either one-way or two-way; either immediate start,
wink start or delay dial. The DID trunks are incoming only and wink start or immediate start.
Some 4ESS switches do not provide secondary dial tone. It is recommended that System 25
provide the secondary dial tone.
Secondary dial tone can be provided through the Automatic
Route Selection (ARS) feature on all DS1 trunks that terminate on the 4ESS switch.
All framing and signaling modes may not be available on some 4ESS switches. However, D4
framing, ZCS line coding, and robbed-bit signaling is supported. Also B8ZS and Common
Channel signaling is supported.
Touch-tone (DTMF) dialing is not supported on some 4ESS switches. Therefore, the System
25 must support both touch-tone and pulse dialing.
The System 25 synchronization should be administered such that the 4ESS switch provides
the master clock source.
5ESS Digital Switch Endpoint
The 5ESS digital switch provides digital central office service and supports “digital” ground
start, reverse battery, and E&M trunk type.
E&M and direct inward dialing trunks are preferred terminations on a 5ESS switch,
The System 25 synchronization should be administered such that the 5ESS switch provides
the master clock source.
AT&T DACS Endpoint
The System 25 DS1 interface can be connected to a DACS endpoint. The DACS can be
thought of as an “electronic patch panel” for DS1 signals. Cross connections may be made
at either the DS1 or DS0 level. The DACS supports both D4 and ESF framing, both ZCS and
B8ZS line coding, and depending on the DACS software version, both robbed-bit signaling
and common channel signaling.
The DACS contains a stratum 3 clock. In all cases, the DACS is synchronized to the AT&T
Reference frequency. Therefore, a suitable synchronization reference may be optionally
obtained from the DACS.
Analog Central Office Endpoint
The System 25 DS1 facility interface may be connected to any analog central office provided
a D4 channel bank is used.
The D4 channel bank is located at the central office and it is the responsibility of the central
office to set the channel unit attenuators to the appropriate values.
If the D4 is a stand-alone unit, it should use the DS1 signal received from the System 25 as
its timing source. In this case the System 25 must maintain a stratum 4 clock. If the D4 is
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