The MCA4 has a lot of capabilities that not all customers may use, and all the features can be disabled to enable a lower price, or switched free by a licence key if a customer buys an upgrade. The key is saved in a EEPROM in the device.

The simplest version has just one ADC, the MCA41.
The MCA42 has two ADCs.
The MCA43 has three ADCs.
The MCA44 has four ADCs.

The MCA4 has four ADCs and the MCA4MCS option, i.e. Multiscaling with one START and two STOP inputs and an external channel advance input. These simpler versions have time stamps in units of msec, so it is not possible to make coincidences with a time window in the µsec range. If the customer wants to acquire dualparamer coincidence spectra for two channels, for two ADCs the 8 ns RTC option is required as the coincidence is recognized by the software when the time stamps of the events are within a coincidence window.

Furthermore, the software checks if the dualparameter licence is enabled in the key, otherwise it will not allow to define dualparameter spectra. This is the MCA4S4 Option. It is not another software, it is only a licence that is defined in the licence key. The MCA4M2 is a MCA42 with two MCA4RTC Options and the MCA4S4 licence. If four ADCs are required for coincidence spectra, four MCA4RTC options are required and the MCA4S5 option. This is the MCA4M4. It includes also a dongle for replay, i.e. offline evaluation of list files. Internal Replay is included already in the MCA4M2 and also in the MCA4M4, so it is possibleto evaluate list files if the MCA4 is connected. The simpler versions can be easy upgraded by a new licence key that can be sent to the customer, so he can do the upgrade by himself.