What is the BRI user rate and its line rate at S/T?

2.048 Mbps user; 192 kbps at S/T

Which describes the U interface?

2-wire loop between NT1 and exchange at 160 kbps with 2B1Q coding

4-wire bus at 192 kbps for 8 terminals

Which are the H channel rates?

H0 = 384, H11 = 1536, H12 = 1920 kbps

H0 = 64, H11 = 144, H12 = 192 kbps

H0 = 384, H11 = 2048, H12 = 1544 kbps

H0 = 16, H11 = 64, H12 = 128 kbps

2071 Shrawan · 5 marks

Interfaces available in ISDN

Short answer

ISDN offers Basic Rate Interface (2B+D, 144 kbps user rate, 192 kbps on S/T bus) over a 2-wire loop, and Primary Rate Interface (30B+D E1 2.048 Mbps or 23B+D T1 1.544 Mbps) on 4-wire. Reference points R (non-ISDN), S/T (4-wire bus), and U (2-wire loop, 160 kbps 2B1Q) define the physical interfaces.

Describe the interfaces available in ISDN.

ISDN offers standard user–network interfaces, defined by the channel structure (BRI and PRI) and by the reference points between functional groups at the customer premises.

1. Basic Rate Interface (BRI) – 2B + D

Two B channels of 64 kbps for voice/data and one D channel of 16 kbps for signalling and low-speed packet data.
User rate $2 \times 64 + 16 = 144$ kbps; with framing and synchronisation the S/T line rate is 192 kbps. On the U interface 160 kbps with 2B1Q coding.
Works over the existing 2-wire telephone loop. Used by homes and small offices.

2. Primary Rate Interface (PRI)

30B + D (Europe, Nepal): 30 × 64 + 64 (D) + 64 (sync) = 2.048 Mbps on an E1.
23B + D (USA, Japan): 23 × 64 + 64 + 8 framing = 1.544 Mbps on a T1.
D channel here is 64 kbps. Used to connect PBXs and LANs. B channels may be grouped into H channels: H0 = 384 kbps, H11 = 1536 kbps, H12 = 1920 kbps.

3. Reference points (physical interfaces)

 TE1 ------------- S --+
                       [NT2]-- T --[NT1]-- U --[LT/ET]
 TE2 -- R --[TA]-- S --+   (PBX)    (NTE)    exchange

Point	Between	Description
R	TE2 and TA	Non-ISDN interface, e.g. RS-232, V.24, analogue
S	TE1/TA and NT2	4-wire, 192 kbps (I.430), up to 8 terminals on a bus
T	NT2 and NT1	Same electrical form as S; S and T combine (S/T) if no NT2
U	NT1 and exchange (LT)	2-wire loop, 160 kbps, 2B1Q (in the USA the NT1 is customer-owned, so U is the network boundary)
V	LT and ET	Inside the exchange

The NT1 converts the 2-wire U interface to the 4-wire S/T bus. The D channel at these interfaces uses LAPD (Q.921) and Q.931 call control messages.

✓ Answer checked by Claude Opus 5.5 (high effort)

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Interfaces available in ISDN

1. Basic Rate Interface (BRI) – 2B + D

2. Primary Rate Interface (PRI)

3. Reference points (physical interfaces)

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