CAB1 batteries?

If both of them beep and the command base doesn't receive, could it be the command base that is the issue?  If you have any PowerMasters, connect one of those to a transformer and see if they receive from the CAB1's.

batteries in these handhelds must be fresh.  if you have a battery checker and it is close to the yellow replace the batteries.  and always replace all of them at the same time.

The problem with the CAB1 and CAB2 is they always have some current draw, even when off.  The soft power switches must have some circuitry running in order to sense power-on.

I always remove the batteries when I am done playing trains. I had one leaker in one of my cab ones I don't need another.

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You could install a small toggle switch on the side of the CAB1, I thought about that more than once.   Failing that, yes, removing the batteries is the only way to drop the power draw to truly zero.

I replace my cab 1 batteries once a year never a problem

OK, I thought I'd actually check this.  I put a 10 ohm resistor in series with a 6.5VDC power supply and powered up the CAB1.  It functions normally from the P/S, and the measured voltage was 6.45 volts to the unit.  I put a scope across the resistor and checked what was going on.  The CAB1 draws 10ma for a couple hundred microseconds every 65ms when idle.  That looks like about 30 uA of average current.  From that measurement, I'd expect standard alkaline AA batteries to last years, not months.  Their rating is typically 2000 ma/hours.  They do discharge in a linear manner, so you probably only get about 1/2 of that useful life before the voltage falls enough to give you problems.

1000ma/hr / .03ua = 33,333 hours.  That's about 3.8 years if my math is correct.  If it's eating new batteries in a month or two, I'd think something is wrong.  Are you sure a button isn't sticking and keeping it on.

The cab1 draws a lot more power when it's active, and after the last button press, it runs for around 20 seconds before dropping into it's sleep mode again.  When a button is active, it has spikes of 50-60 ma, so it's clearly consuming a lot more power in that mode.

After any button push, i think the CAB1 periodically turns on the LEDs in the optical encoder (red knob) to see if the knob has been moved.  If it detects motion, then it goes into an active mode that reads the knob rapidly.

If John is kind enough to determine the minimum voltage, it will be the lower limit for operation of the red knob.  Any measurement with a power supply would be the LOADED voltage coming out of the batteries, not the terminal voltage when no load is applied.  (Some voltmeters have a position for battery testing that puts a moderate load on the battery.  This would be better than an unloaded voltage measurement.)

I tested it with a DC power supply connected and monitoring the current by use of the 10 ohm resistor.  I didn't think to start lowering the voltage, and I didn't have the base out anyway.  My mission was to find out what the current draw was when it was sleeping.   When you push a button, it wakes up for 20 seconds, then goes back to sleep.  From my tests, I don't see why the CAB1 would run a set of batteries down sitting on the shelf in a month or two.  Maybe next time I get energy, I'll test the other CAB1 to see if there's a difference in them.

You're right about the batteries, measuring them with no load doesn't tell you much.  I typically use a 22 ohm resistor to load a battery and test it's voltage to determine if it's good.

"I don't see why the CAB1 would run a set of batteries down sitting on the shelf in a month or two."

but do not forget to take into consideration usage.  any usage will lower the available power.  My cab2 goes through batteries about once a month, but I use it every week for 6 plus hours at the club plus a few hours at home. 

I can not keep my hands off the horn.

Obviously, usage will use up the batteries, I was just investigating the possibility that it would run down the batteries when sleeping.

I see spikes of fairly high current when it's actively sending keys to the base, that will certainly use batteries.