Operating instructions

2-12 Overview
MB*/* Installation and Operation Manual
Return Path, RA-Kit/H or RA-Kit/L
The circuit board of the MB*/* amplifier accommodates the optional return path. The return
path kit, Model RA-Kit/H or RA-Kit/L, includes the return amplifier hybrid (illustrated in
Figure 2-15) and jumpers. This equips the MB*/* to pass signals in the return or upstream
direction. The standard circuit board contains all components including the diplex filters, with
extended return bandwidth, for the amplifier input and output.
Optional SRE-*-* return equalizers compensate for cable attenuation and are available in 1 dB
increments for S-split, and 2 dB increments for all other splits, from 0 dB through 12 dB. All
items are plug-in and easily installed.
There are JXP-*B pad facilities located at the input and output of the return path. You can use
these pad facilities as test points or signal injection points. The output pad value is normally
selected to control the return signal level into the next upstream amplifier. Select an
appropriate input pad to attenuate excessive input signal.
The return-input test points and the return-output test point are −20 dB directional couplers.
These test points present 75-ohm source impedance and do not require special test probes.
Ingress Control Switch
The ingress control switches (ICS) (illustrated in Figure 2-15) provide return-path signal
attenuation or cutoff in the MB*/*. The dual output MB*/* requires two ICS’s. Switching is
accomplished through the frequency agile LIFELINE Flexstat 3 status-monitoring module,
LL-MB-F3, located in the housing lid next to the power supply, as illustrated in Figure 2-14.
The ICS provides a means of isolating sources of ingress from a centralized location. Using a
downstream command through the LIFELINE status-monitoring system, you can attenuate the
return path through the amplifier by 6 dB or by 38 dB. By reducing the ingress level at the
headend or monitoring point, you can further isolate the ingress source.
After you isolate an ingress source to the last possible amplifier, node, or line extender, you can
shut the return path off at that location. This limits the impact of the ingress on the remainder
of the network while eliminating the source of ingress.