While PBX may have many components for performing telephone exchange activities, but there are some components which are very important and are a must for a PBX machine and are present in any type of PBX machines irrespective of their make, model or brand. They are :-
Like a PC, PBX too contains a CPU ( Central Processing unit) which controls all switching activities, routing of calls, call logging, connect, disconnect etc. It performs all the logic and normally controlled by a power MCU ( Micro Controller Unit). Many manufacturers design CPU as a plugin in card so that it could be installed in PBX cabinet easily.
2. Power Card
Another important module or component of any PBX system is power card or power supply module. Power supply is important module as it gives output of -48V/-24DC DC which is required to supply to telephone instrument for dial tone, ring tone etc. The capacity of the power supply unit depends on number/capacity of extension lines of the PBX. It is normally designed a plugin card or built into the PBX cabinet.
3. Line Cards
Line cards are modular units which could be plugged in to PBX cabinet in order to increase number of extension lines. This is very important modules as it provides the connect to the telephone instrument at user end. By making them modular, PBX can have future upgrade facility and reduce initial cost to the customer.
4. Operator Console
Operator console is a telephone line instrument which could be used to control incoming calls, routing incoming calls to extensions by a human intervention. It is an useful component used by a telephone operator or a human receptionist.
5. Trunk lines
Trunk lines are the connection to the outside world of the PBX. It can be both digital or analog. Analog trunk lines are analog telephone lines from PSTN. When it is digital, it uses digital interfacing technology like ISDN, SS7 etc. Normally, high end PBX which needs more trunk lines use digital standard and lower end PBX uses analog lines.
Apart from these, telephone instruments, wiring, UPS ( Uninterrupted Power Supply), earthing arrangement are important part of any PBX system.