Toshiba CTX28 manual Capacity and Cabinet Slot Information

ISDN Interfaces

RBSU/RBSS Interface Units

The RBSU, and/or RBSS circuits that connect to the Strata CTX station side, (BRI-NT, S- reference point) allows direct connection of multiple ISDN (TE-1 or TA) devices. The S point of the RBSU/RBSS supports the Toshiba Strata CTX passive bus, also known as point-to-multipoint connection. The terminal-side (S-point) of the RBSU/RBSS BRI circuit can have parallel connections of up to two TE-1s or TAs maximum.

When multiple TE-1 and TA devices are installed on a single RBSU/RBSS BRI circuit, the devices must share, or contend for, that circuit’s two B-channels. That is to say, a maximum of two simultaneous voice and/or data calls are allowed between both devices connected to the same BRI circuit. The contention rule for the two BRI B-channels is first come, first serve.

3336	BRI-NT	BRI-TE	BRI
	(4-wire)	(4-wire)	(2-wire)

ISDN Interfaces

1

2	TE-1	RX		RX
	or		DK TBSU or	NT1	RX/TX
	TA		RBSU/RBSS
TE-1		TX		TX
or
TA

STU

S, T, and U are ISDN reference points.

TE = S-type Terminal Equipment

TA = S-type Terminal Adaptor

PSTN

Figure 7-9 RBSU/RBSS Interfaces between the S/T Reference Points

Capacity and Cabinet Slot Information

The RBSU/RBSS can be installed in any slot except in a slot that has been left vacant to provide capacity for RDTU, BPTU or RPTU2 or RPTU as shown in Table 2-54 on page 2-39and Table

2-55 on page 2-40. Each RBSU and/or RBSS contains two circuits and each circuit reduces the system capacity by two station ports and two CO lines (one port/line per B-channel). Therefore, if the RBSU PCB is installed, the station port and CO line count will increment by four ports and four lines at the RBSU cabinet slot.

If the RBSU/RBSS is installed, the station port and CO line count will increment by eight station ports and eight lines at the RBSU/RBSS cabinet slot. RBSU and RBSS PCBs can be installed in any combination so long as the number of RBSU PCBs is the same or greater than the number of RBSS PCBs. See “ISDN BRI Digital Station PCBs” on page 2-41and “Worksheet 3: CO Line” on page 2-25for the maximum BRI circuits allowed.

Strata CTX I&M 06/04 7-15