Rated 
Started Jul 12, 2004
Strengths: Very sensitive! Extremely clear and strong signal. No interference! Parents unit uses either A/C adapter or rechargeable battery.
Weaknesses: Receiver (parents unit) includes Ni-Cad rechargeable instead of NiMh or better. Transmitter (babies unit) only works with A/C adapter (no batteries).
This is a very good monitor. Right out of the box, we had it set up and working perfectly in about two minutes. Our baby's room is fairly small 10' x 11' . At first, I placed the transmitter right next to the crib because I thought that it would be better able to pick up any baby sounds. However, I quickly realized that this unit is EXTREMELY sensitive. Since my wife didn't want the wire from the AC adapter to be visible, I've since moved the transmitter to the opposite corner of the bedroom, atop the changing station/dresser. It picks up and transmits even the quietest little noise our baby makes from the crib (nearly 14 ft. away). I've stood by the crib (again, on the opposite side of the room from where we now have the transmitter placed) and spoken ever so softly and my wife has heard me perfectly well from our room on the other end of our 2600 sq. ft. house.
I've also taken the portable receiver outside of our home and walked around to the back of our yard and out to the street in front of the house and only lost the clear signal when I crossed the street.
The parents unit can be set to receive a constant signal or it can be set on "voice activation" mode. We usually keep it on the latter so that we only get a signal when the baby is stirring. The volume can be adjusted on the parent unit to any desired level.
The system includes an "out of range alarm" so that if for any reason you lose the signal from the transmitter, an alarm notifies you that you're no longer in contact with the baby unit.
There are 27 channels to choose from in case you experience any interference from another 900 mhz system operating nearby. We use two different 900 mhz phones in our house (one Sony and one Uniden) and neither has interfered with the baby monitor. We simply left the baby call units set on the default setting from the factory.
I believe that if you're not going to want to move the parents unit around much, the less expensive 9-channel unit (NTM-900) would be just fine. I purchased this unit because we frequently use our outside patio area and I wanted the battery operated option that comes only with the slightly more expensive NTM-910.
Lastly, Sony chose to include a proprietary rechargeable Ni-Cad battery pack with a two-pronged plug for the parents unit. It's nice that the unit can simply be plugged into the AC adapter and run from that as it charges the battery. When unplugged from the AC adapter, the battery kicks in after a second or two delay.
I think that two improvements could be made that would make this system better. First, Sony could have included NiMH batteries so that the unit could be plugged back in at anytime without diminishing the operating time inherent with Ni-Cad batteries that are recharged before they are completely drained. Second, we frequently experience brown-outs (a temporary loss of electricity) in the summer time. When this happens, the baby unit becomes non-functional since there is no battery back-up. It's nice that we can be awakened by the alarm on the parents unit at the loss of the signal but it would be nicer still if we weren't awakened unnecessarily simply because they chose not to include the battery backup.
If we are still using this monitor when the Ni-Cad battery dies, rather than purchasing Sony's replacement proprietary battery pack, I intend to remove the plug from the original Sony battery pack and solder it onto my own pack that I will make, using two AA NiMH batteries. That will solve one of Sony's shortcomings with this unit. As for the lack of a battery backup on the baby's unit, I'm thinking about adding my own backup battery system (like the ones used with computers) if I can find one for a few bucks.
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