A work platform for a ladder includes a support assembly that removably attaches to the ladder. An electronic control system includes a controller performing an air-conditioning control so that flow detected information from a hot-wire flow sensor, refrigerant operation state information from a refrigerant operation state sensor, and temperature information from a resistance value sensor are added in external information detection means. The femtocell may select, based on the received messages, a master clock within one of the plurality of different sources as a master clock for synchronization of the plurality of different sources. Thus, the commands are issued concurrently on different channels. A combined indicator is based on an addition of the pause term and the motion term.