Parallel Operation with Manual Push Buttons (Parallel Manual Control)
Connecting the relay contacts of the radio remote control receiver in parallel with the same control line, without removing the existing hard-wired push button installation. On the ST100 and SF100 sets it is stated that manual push buttons and the RF remote control can be used together; that way, if the remote control fails, the machine keeps working with the hard-wired button.
In a parallel connection, the receiver's dry contact is bridged between the same two points as the hard-wired button's contact. Electrically the two switches are in a logical OR relationship: whichever one closes energises the contactor coil. Since no change is needed in the hard-wired installation, the retrofit mostly ends with a few added conductors inside the panel.
This arrangement brings two rules:
- The risk of commands from two sources at once: if one gives forward and the other reverse, the contactors clash. Electrical and mechanical interlocking is therefore indispensable.
- Clear responsibility: the operator must know which control is authorised on the machine at that moment; two operators giving commands to the same machine from different directions must be prevented.
On the emergency stop side, parallel operation is not a convenience but a requirement: the machine's hard-wired emergency stop circuit remains the primary one and must be able to cut the movement independently of the state of the radio remote control. During commissioning, first test both control paths separately without load, then verify the interlocks.
The context in which this term is used: Wireless Crane Remote Control Selection Guide