The TX-111 is the latest design remote for the Dynatron 3 Series (AKA Cyclops P355, P375, P385). The remote is powered by 2 CR2016 Coin shaped batteries. Typically I would expect the batteries to be good for around 3 year, however excessive usage may shorten this time.
To change the batteries the remote case can be opened by using a flat blade screw driver to prize the case apart. Care should be taken not to bend the + terminal that holds the batteries in place as doing so may cause a loose contact.
I’ve now lost count of how many TX-111 remote controls I’ve seen where the battery terminals become lose or have a poor contact. The good news is that it’s normally an easy fix. If the remote does become intermittent then it is worth using your thumb to bend the + terminal down after making sure the contacts are clean.
If you are after a replacement then I suggest TX-90 remote as a alternative. Whist it is designed for the 7 series it also works with the 3 series of alarms and although it costs $10.00 extra, is more reliable and in my opinion a nicer design.
Replaces old TX-11 remote