The signalman has a busy day at the station. The system looks to be electro-mechanical but still has a bit of manual operations to it with the levers.
You're right. Even each levers had special keys for preventing false handle movement, which are part of default equipments for the current mechanical signalling system. In North Sumatra operation region, however, there is a modernized mechanical signalling system with fully-computerized interlocking system, allowing a smoother operation for lines still equipped with mechanical signals (though it is now a common practice for replacing mechanical signals with electric signals, but at least this solution was deemed to be economical for safer operation in the transition period).
I watched another video by the same guy that showed the level crossings being operated. There were two operations the manual one with an older gent turning a wheel to open and close the gates and another that was automated.
For the grade crossing, the ones operated with a rotating handle (labeled as "hand generator") is commonly found on those with less frequent road traffic density, though sometimes this type is also used at main roads in the rural area. On the other hand, the automatic ones with switches and buttons are mostly used on grade crossings where the road traffic had high traffic density (or even congested), and for safety measurements they are equipped with "boom gate brake button" for temporarily stopping the boom gate in particular durations (normally it is used for clearing road vehicles trapped inside the crossing). However, if the crossing is located right inside or near the station, the equipments for operating the crossing are placed inside the station's signal operator room (even those who operated the crossing are station personnels, including the signalman).
Beside the common ones, there are also crossing that are still operated using mechanical handle connected to the boom gate with steel cable and chain, though they are slowly replaced by the automatic ones. Even many unofficial crossings made by local people are found equipped with boom gates made of bamboo (painted in red and white stripes) and connected with a rope between one each other (many of them were later closed by both Indonesian Railways and local government for increasing safety measurements, since grade crossing accidents are one of the serious problem faced by Indonesian Railways in the past, and even today).
========================
And here is another one from me:
https://www.google.com/maps/@-6.256...4!1sWNjPlZoNrMVRM4i6kc8CbA!2e0!7i13312!8i6656
This one was photographed on March 2018, with a 205 series EMU of former East Japan Railway Company trainset 205-122 (former trainset HaE 14 of Kawagoe Depot) seen here serving the down commuter train (probably toward Rangkasbitung, though it is probably the ones that terminates at Parung Panjang station and returns back to Tanah Abang station). Previously there was a grade crossing here, but it was replaced by an overpass after a horrific grade crossing accident occurred on December 9th, 2013, when former Tokyo Metro 7000 series EMU trainset 7121 as commuter train number 1131* slams into a gasoline-carrier truck and causes fire with explosions due to leakage of gasoline load from the truck, where 7 fatalities were recorded (including the three train crews that serves the train). Ironically, the former grade crossing where the 2013 accident occurred is not far from the site of tragic head-on collision occurred on October 19th, 1987, where negligence of signalman caused two trains packed with lots of passengers to collide and took 156 fatalities (which is the worst accident in the history of railways in Indonesia to date).
*
the train number is now used by one of Bogor Line commuter train that serves Bogor - Jakarta Kota corridor