The Abacus application can be used for a Master POS, a Slave POS, or a Waiter Pad; you just need to reconfigure the settings.
Different settings are required for different uses, with different capabilities.
The Master POS is what you set up in the initial stages. It has the full capabilities of the Abacus POS application; there is nothing a Slave POS or a Waiter Pad can do that the Master POS cannot do.
However, there can only be one Master POS, as that is what the terminals (Slave POS and Waiter Pad devices) will need to communicate through.
Below is a comparison of the navigational screens of each setting to give you a general idea of the functions available to each device.
If you are using several terminals, your Master POS device must be running at all times, so the Slave devices can communicate with it. In the Master POS device settings (the iPad settings rather than the Abacus settings), go to General > Display & Brightness > Auto-Lock and set it to Never.
Any device that is not the Master is a Slave. A Slave POS can still take orders and complete transactions. It has most of the same functions as the Master, but it must be a Slave in order to communicate with the Master and - through the Master - other Slaves.
The Slave POS setting is designed for fixed Point of Sale terminals, the regular iPad or iPad Pro.
A Waiter Pad is also a Slave, but a limited type of Slave. Its main difference is although it can take orders, it cannot complete transactions. For this reason it is distinct to the Slave POS.
The Waiter Pad setting is designed for iPads that are carried around the restaurant by hand.
You can still use a Slave POS for payment on the dining room floor, just don't turn on the Waiter Pad function