3
T
HEORY OF
O
PERATION
The ICRI-2PE and ICRI-2PED are limited function versions of the ICRI (P/N 500.9250). These
units can provide a communications bridge, or link, between two public safety agencies with
otherwise incompatible radios. The ICRI-2PE and ICRI-2PED can quickly establish the link as a
tactical situation rapidly unfolds. As with all ICRIs, they require minimal resources to move it
into place, to enable it initially, or to maintain its operation over many hours. The units will
provide full operational capabilities moments after arrival on-scene, and then remain operational
for 30+ hours powered by 6 internal “AA” batteries.
The ICRI-2PE and ICRI-2PED perform two primary functions for public safety personnel:
Distributes the audio received from one two-way radio, handset/headset, or telephone, to
other devices connected to the unit.
Utilizes this same incoming audio to “key” the other radios or telephones connected to
the ICRI.
The radios can be portables, mobile, SPRINT “Direct Connect” phones or a
combination. Land-line telephones, cell phones, STU, STE or satellite phones can also be
connected to the ICRI.
The ICRI-2PE and ICRI-2PED do not discriminate or evaluate the incoming audio, so that
unnecessary delays are not inserted into the audio transfer or “keying” processes. Radios,
telephones and/or recording devices connected to the ICRI are provided with the incoming audio,
essentially in real-time. A “buffer” preserves the first syllables of incoming audio while the
transmitters are keying up “trunking” radio systems to provide radio channel access.
These versions of the ICRI contain 2 circuits that key the radios connected to the ICRI; these
circuits are commonly referred to as “VOX” or “voice-activated switches.” The ICRI uses these
circuits to perform other controlling functions as well. Only the VOX directly connected to the
incoming audio is used to key each of the other radios simultaneously (all other are temporarily
disabled, preventing a second “voice” from causing a disruption of communication).
All the ICRI’s radio connections/ports are “universal”; any radio can be connected to any port
without special adjustment. Radio interconnect cables provided with the ICRI are engineered for
the radio brands/models, and, along with circuitry within the ICRI, adjust for the difference that
may exist between radios.
Initial connection of voice devices is aided by LED indicators for each connection/port. The
LED is an indicator of audio input to the ICRI and is used to initially set the radio output level to
the ICRI. This adjustment is made without meters or other instruments; an Automatic Level
circuit in the ICRI, that requires no user involvement, aids in this.
Connection of mobile radios to the ICRI will not prevent the regular operation of the mobile
radio’s hand microphone. This capability is derived from the design of the C-AT-supplied, radio
interface cables.
