Recommendation X.10
 CATEGORIES OF ACCESS FOR DATA TERMINAL EQUIPMENT (DTE) 
TO PUBLIC DATA TRANSMISSION SERVICES
(Malaga–Torremolinos, 1984; amended at Melbourne, 1988)
	The CCITT,
considering
	(a)	that Recommendation X.1 defines the international user classes of service in public data networks (PDNs) and ISDN;
	(b)	that Recommendation X.2 defines the international user services and facilities in PDNs;
	(c)	that Recommendation X.3 defines the Packet Assembly/Disassembly facility (PAD) in packet switched public data networks;
	(d)	that Recommendation I.411 defines the reference configurations for access to ISDN services, including Terminal Adaptor (TA) functional grouping;
	(e)	that Recommendations X.30 (I.461), X.31 (I.462) and the I.230 series, define the circuit switched and packet switched data transmission services available from ISDN (including through Terminal Adaptors);
	(f)	the desirability for the users to have defined the various possibilities and requirements for accessing the different public data transmission services,
unanimously recommends
	that categories of access for data terminal equipment (DTE) to the data transmission services provided by PDNs and by ISDNs through Terminal Adaptors should be as defined in this Recommendation.
1	Scope
	This Recommendation defines the different categories of access for data terminal equipment to the different data transmission services provided by public data networks (PDNs) as defined in Recommendation X.2 and by ISDNs (including through Terminal Adaptors) as defined in Recommendations X.30 (I.461) X.31 (I.462) and the I.230 series, namely:
i)	circuit switched data transmission services;
ii)	packet switched data transmission services;
iii)	leased circuit data transmission services.
	The categories of access described in this Recommendation take into account direct connections (see Note) to public data networks and ISDNs and the various access cases where interworking with other public networks is involved. Access to the packet switched data transmission service via the PAD function as defined in Recommen-dation X.3 is also covered in this Recommendation.
	Note – Direct connections may be provided by means of leased circuits or by dedicated access circuits.
2	General
	Access for data terminal equipment to data transmission services may be achieved by either of the following (see Note):
a)	by direct connection of the DTE to the public data network or ISDNs;
b)	or by switched connection of the DTE to a PDN via an intermediate public network of another type (including a PDN, PSTN or ISDN);
c)	or by switched connection of the DTE to an ISDN (including through a Terminal Adaptor) via an intermediate public network of another type.
	For example, packet mode terminals may access the public packet switched data transmission service, in user classes of service 8 to 11, either directly or via a switched connection. The switched connection will be established using a circuit switched data network or a public switched telephone network. In both switched cases an interworking function will be required to access the packet switched data transmission service.
	Note – It is not mandatory for Administrations to provide all the categories of access contained in this Recommendation.
3	Categories of access
	§ 3.1 specifies the categories of access to the data transmission services provided by PDNs for the direct connection case.
	§ 3.2 specifies the categories of access to the data transmission services provided by PDNs for the switched connection case.
	§ 3.3 specifies the categories of access to the data transmission services provided by ISDNs through Terminal Adaptors for the direct connection case.
	§ 3.4 specifies the categories of access to the data transmission services provided by ISDNs through Terminal Adaptors for the switched connection case.
3.1	Direct connection to data transmission services provided by public data networks
TABLE 1/X.10
Start–stop direct connection to a circuit switched data transmission service (see Notes 1 and 2)
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
A1 
A2	 50 to 200 bit/s
300 bit/s	 See Recommendations X.20 and X.20 bis	
TABLE 2/X.10
Synchronous direct connection to a circuit switched
data transmission service
(see Note 1)
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
 B1	    600 bit/s		
B2	  2 400 bit/s		
B3	  4 800 bit/s	 See Recommendations X.21 and X.21 bis	
 B4	  9 600 bit/s		
B5	 48 000 bit/s		
B6	 64 000 bit/s		

TABLE 3/X.10
Start–stop direct connection to a packet switched
data transmission service
(see Notes 1 and 2)
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
 C1	110 bit/s		
C2	200 bit/s		
C3 	300 bit/s	See Recommendation X.28	
 C4	200 bit/s		
C5	75/1 200 bit/s		
C6	2 400 bit/s		
TABLE 4/X.10
Synchronous direct connection to a packet switched
data transmission service
(see Note 1)
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
 D1 	2 400 bit/s		
D2	 4 800 bit/s	 See Recommendations X.25 and X.31	
 D3 	  9 600 bit/s	(case A)	
D4 	 48 000 bit/s	(see Note 3)	
D5	64 000 bit/s		
TABLE 5/X.10
Start–stop direct connection to a leased circuit
data transmission service
(see Note 2)
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
E1
E2	50 to 200 bit/s
300 bit/s	See Recommendations X.20 and X.20 bis	

TABLE 6/X.10
Synchronous direct connection to a leased circuit
data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
 F1	    600 bit/s		
 F2	  2 400 bit/s		
 F3	  4 800 bit/s	 See Recommendations X.21 and X.21 bis	
 F4	  9 600 bit/s		
 F5	 48 000 bit/s		
3.2	Switched connection to data transmission services provided by public data networks
TABLE 7/X.10
Synchronous switched connection by means of the PSTN
to a circuit switched data transmission service
	For further study.
TABLE 8/X.10
Start–stop switched connection by means of a CSPDN
to a packet switched data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
 K1	 300 bit/s	 See Recommendation X.28	
TABLE 9/X.10
Start–stop switched connection by means of the PSTN
to a packet switched data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
 L1	110 bit/s		
 L2	200 bit/s		
 L3	300 bit/s	See Recommendation X.28	
 L4	200 bit/s		
 L5	75/1 200 bit/s		
 L6	2 400 bit/s		
TABLE 10/X.10
Synchronous switched connection by means of a CSPDN
to a packet switched data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
 O1	2 400 bit/s		
 O2 	  4 800 bit/s		
O3 	  9 600 bit/s	 See Recommendation X.32	
O4 	 48 000 bit/s		
O5	 64 000 bit/s		

TABLE 11/X.10
Synchronous switched connection by means of the PSTN
to a packet switched data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements	
 P1	1 200 bit/s		
 P2 	 2 400 bit/s		
P3 	 4 800 bit/s	See Recommendation X.32	
P4	 9 600 bit/s		
TABLE 12/X.10
Synchronous switched access by means of an ISDN B channel
to a packet switched data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements at		
		 Reference point S/T	 Reference point R	
 Q1 	2 400 bit/s			
Q2 	  4 800 bit/s	See Recommendation X.31		
Q3	  9 600 bit/s	(case A)	See Recommendation X.32	
 Q4	 48 000 bit/s	 and Recommendation X.32		
 Q5	 64 000 bit/s			
3.3	Direct connection to data transmission services provided by ISDNs (including through Terminal Adaptors)

TABLE 13/X.10
Synchronous direct connection to a circuit switched
data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements at		
		 Reference point S/T	 Reference point R	
 S1	600 bit/s 			
 S2	 2 400 bit/s			
 S3 	  4 800 bit/s	See Recommendation X.30	See Recommendations X.21 and X.21 bis	
S4	9 600 bit/s 			
 S5 	48 000 bit/s			
S6	64 000 bit/s			
TABLE 14/X.10
Synchronous direct connection via the ISDN B channel
to a packet switched data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements at		
		 Reference point S/T	 Reference point R	
 T1	2 400 bit/s 			
 T2 	4 800 bit/s	 See Recommendation X.31 (case B)	See Recommendation X.25	
T3 	9 600 bit/s			
T4 	48 000 bit/s 			
T5	64 000 bit/s			
TABLE 15/X.10
Synchronous direct connection via the ISDN D channel
to a packet switched data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements at		
		 Reference point S/T	 Reference point R	
 U1 	2 400 bit/s			
U2 	4 800 bit/s			
U3 	 9 600 bit/s			
U4 . 	48 000 bit/s (see Note 4)	See Recommendation X.31	 See Recommendation X.25	
U5	64 000 bit/s (see Note 4)			

3.4	Switched connection to data transmission services provided by ISDNs (including through Terminal Adaptors)
TABLE 16/X.10
Start–stop switched connection by means of the PSTN
to a packet switched data transmission service
	For further study.
TABLE 17/X.10
Synchronous switched connection by means of a CSPDN
to a packet switched data transmission service
	For further study.
TABLE 18/X.10
Synchronous switched connection by means of the PSTN to a packet switched data transmission service
	For further study.
TABLE 19/X.10
Synchronous switched connection by means of an ISDN B channel
to a packet switched data transmission service
Category of access	 Data signalling rate	 DTE/DCE interface requirements at		
		 Reference point S/T	 Reference point R	
 Y1 	  2 400 bit/s 			
Y2 	 4 800 bit/s			
Y3 	  9 600 bit/s 	See Recommendation X.31 (case B)	 See Recommendation X.25	
Y4	48 000 bit/s 			
Y5	64 000 bit/s			
 Note 1 – Direct connections may be provided by means of leased circuits or by dedicated access circuits.
Note 2 – Some Administrations may offer the categories of access of 600 bit/s, 1200 bit/s, 2400 bit/s, 4800 bit/s and 9600 bit/s.
Note 3 – Recommendation X.31 (case A) is appropriate at the S/T reference point when category of access D5 is provided by means of ISDN B channel.
Note 4 – For 64 kbit/s D channel only.