IBM 3745 Series, Hardware Maintenance Reference

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Surge Protection
1. Primary protection: a telephone line surge protection (carbon block or gas
tube) should also be provided by the line connector before the DCE wall plug.
2. Secondary protection: three protection devices connected from tip to frame
ground, from ring to frame ground, and tip to ring.
In the countries where it is authorized, this limits the maximum voltage to 80 V
peak (line to ground) or 80 volts peak (line to line). In addition, the transformer
saturation characteristics, and the Zener diode network across the line trans-
former secondary windings, limit the maximum peak voltage to 12 V (line to
ground).
Transit Time
The transit time is the time that elapses between the input of a bit in the local trans-
mitter and the output of this bit from the remote receiver, assuming a zero trans-
mission delay over the telephone line.
Modulation type
Transit time (ms)
14 400 12 400 9600 7200 4800 2400
IBM Native 21.4 21.4 17.2 18.0
CCITT V.33 21.4 21.4
IBM Native 18.0 18.0
CCITT V.29 16.8 16.8 16.8
IBM Native 17.4 21.4
CCITT V.27 bis 12.2 15.6
RFS Delay
The RFS delay is 2 ms for LICs type 5 in any configuration. It must be added to
the transit time to evaluate the turnaround time.
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IBM 3745 Models 130, 150, 160, 170, and 17A: Hardware Maintenance Reference