YTD428_07 YAMAHA [YAMAHA CORPORATION], YTD428_07 Datasheet - Page 16

• Manufacturer Part Number: YTD428_07
• Description: IDSU ISDN DSU for Terminal Equipment
• Manufacturer: YAMAHA [YAMAHA CORPORATION]

4.3 Interface Switch Section
Normally, this section connects T I/F section with CT/LT section to provide DSU function (NTSEL = “H”).
By setting this section, the driver/receiver function of the T I/F section can be separated from the CT/LT
section and be used independently (NTSEL = “L”).
For example, it is useful under such a situation that there are some terminals which have DSU function on
the same S/T line.
In case of using NTSEL = "L" (TE mode), the signals of TA/TB and RA/RB should be reversed by switches
or other devices. Because S/T bus signals that are connected to TA, TB, RA and RB pin are different between
using YTD428 as DSU (NTSEL = "H") and S/T terminal (NTSEL = "L").
terminals that are connected with the same bus don't require the terminal resistors. Therefore, it is useful that
switches which can control ON/OFF of the terminal resistors are provided on the equipment.
Generally speaking, the terminal resistors are only mounted on the nearest terminal from DSU and other
RA / RB
TA / TB
Figure 4.1 Image Of Using T Ref. Pt. I/F Drive/Receiver Independently
pt. I/F
T ref.
TTL I/F
YTD418 or
Layer 3 information
YTD423
(Bch data)
switch
I/F
YTD428
(No transformer is required)
Call control
and
CT
LT
circuit
U ref. pt.
driver
U ref.
pt. I/F
DSU section
L1
L2