Specifications

Chapter 6 TR-08 Option
6-6
CONFIGURATION SWITCHES FOR TR-08 OPERATION
Since the TR-08 option on the Access Bank I effects the operation of the Line Interface Unit
(LIU), the interpretation of some of the configuration switches have changed.
Front Panel DIP Switches
Note for front panel DIP switches, the On position is towards the silk-screened top of the Access
Bank I chassis.
DIP Switches 4, 8, and 9 are CHANGED from Access Bank I D4/ESF Operation
1 (LBO -7.5dB)
2 (LBO -15dB)
3 (Clock Source)
4 (T1 Framing)
5 (T1 Line Code)
6 (CSU on/off)
7 (Test Tone)
8 (BPV Threshold)
9 (BPV Threshold)
10 (Option 10—Not Used)
Switches 1 and 2: Line Build Out (LBO)—On is Enabled, Off is Disabled
Commonly, LBO is set for 0dB since TR-08 units are not typically deployed next to the switch.
This attenuation setting can be adjusted in the field as a method to improve line quality when
required.
Switch 3: Clock Source—Off is Slave, On is Master
Switch 3 specifies the clock source used to derive timing for the unit’s digital operation. In the
Off position, the clock source is slaved off of the T1 line, whereas in the On position, the Access
Bank I uses an internal Stratum 4E master clock source. Typically the master setting (On) is
only useful in private point-to-point networks. For TR-08 operation, the clock source is typically
slaved from the T1 line since it’s timing is derived from a more accurate upper stratum clock
source.
Switch 4: T1 Framing—On is Shelf B/C/D, Off is Shelf A
Configuration switch 4 is normally used on the Access Bank I to select D4 or ESF framing.
Under TR-08 operation, this switch specifies whether the Access Bank I is operating as a “Shelf
A” (Switch 4 is Off) or as a “Shelf B/C/D” (Switch 4 is On). The switch 4 assignment of RTs to the
shelf A or shelf B/C/D setting must match the characteristics of the T1 line connected to the RT.
These T1 line characteristics are specified by the CO switch translation tables. See Figure 7-5
below for a diagram of T1 framing settings.