IBM SY44-5902-05 manual Communications signal voltage levels

Communications signal voltage levels

Table 88. Communications signal voltage levels

Interface type	OFF voltage level	ON voltage level
V.24	Less than -3 volts	More than +3 volts
EIA-232
X.21bis
V.35	When terminated by a 100-ohm resistive	When terminated by a 100-ohm resistive
	load, the differential voltage (A-B) is 0.55	load, the differential voltage (B-A) is 0.55
	volts +/- 20%.	volts +/- 20%.
Note: See the V.35 cable to find out which pin numbers are A and B.
X.21	The differential voltage (A-B) is less than	The differential voltage (A-B) is more than
	-0.3 volts.	+ 0.3 volts.
	When terminated by a 100 ohm resistive	When terminated by a 100 ohm resistive
	load, the differential voltage (B-A) is the	load, the differential voltage (A-B) is the
	larger of 2.0 volts or 50% of the open	larger of 2.0 volts or 50% of the open
	circuit voltage. The open circuit voltage is	circuit voltage. The open circuit voltage is
	between 2.0 and 6.0 volts.	between 2.0 and 6.0 volts.
Note: See X.21 cable diagram to find out which pin numbers are A and B.
ISDN	Logic 0	Logic 1
	The differential voltage (A-B) is less than	The differential voltage (A-B) is 0.0 volts
	+.75 volts and more than -.75 volts	(nominal).
	(nominal).

Chapter 9. System Architecture and Configuration 267