Cellphone-Mate Phone Amplifier / Antenna Coupler entitles you to efficient reception Usage: Essentially, the purpose of a coupler is to split signals (like a splitter) but focuses them more in one specified region. If you wanted more power concentrated into a corner of your building, then installing a coupler will be the ideal thing for you to do. To install, a coaxial cable would be inserted into the input and the other end will go to the "inside" side of the amp. Those two outputs will be connected to interior antennas with the coupler output being the main bulk distributor and the other output being the less amplified port. Explanation: Every coupler has 2 outputs (coupler output vs. output) with different levels of loss. These outputs will be connected to antennas whether outside or inside. Depending on how you want to distribute the signals and how little loss you want on one specific side, that will be the key to differentiating which coupler best suits you. Basically look at the value (signal distributed) and the admeasure (signal loss). As you go up in value, the signal loss decreases. Example: a -5 dB coupler will distribute plus or minus 5 dB of signal from an antenna / amplifier to the area you concentrate it on. However that means the other output end that goes somewhere else will have a guaranteed signal loss of 1.65 dB causing that other area to be less receptive. Check this out: [ VERY USEFUL SIGNAL CALCULATOR ] & [ FAQ A.G. AMPLIFIER'S GUIDE FOR NEWBIES ] Phone Amplifier / Antenna Coupler features Standards supported: all major standards include- CDMA, GSM, GPRS, TDMA and AMPS, iDEN Nextel Neworks Type: -5 dB Electrical Parameters Value -5 dB Frequency range 800-2500 MHz 700-800 MHz 2500-2700 MHz Insertion Loss 0.4 dB 0.5 dB 0.5 dB Admeasure Loss 1.65 dB Coupling port Loss 5±0.5DB 5±1DB 5±1DB Impedance 50Ω     VSWR ≤1.30     Maximum Power 100W     Connector N Female     Work Temperature -30 ~ +65 degree C     Size (mm) 120 x 40 x 17 mm (NO Connectors)     Color Spray painted black     *Life Time Warranty available with Cellphone-Mate Cellphone-Mate Antenna / Amplifier Coupler 5 dB