Telecommunications Access Method (TCAM) is an access method

Access method

An access method is a function of a mainframe operating system that enables access to data on disk, tape or other external devices. They were introduced in 1963 in IBM OS/360 operating system...

, in IBM's OS/360 and successors

OS/360 and successors

OS/360, officially known as IBM System/360 Operating System, was a batch processing operating system developed by IBM for their then-new System/360 mainframe computer, announced in 1964; it was heavily influenced by the earlier IBSYS/IBJOB and Input/Output Control System packages...

 computer operating systems on IBM System/360 and later, that provides access to terminals units within a teleprocessing network.

TCAM provided essentially the same functionality as QTAM, and in addition was the access method for the initial version of Time Sharing Option

Time Sharing Option

In computing, Time Sharing Option is an interactive time-sharing environment for IBM mainframe operating systems, including OS/360 MVT, OS/VS2 , MVS, OS/390, and z/OS.- Overview :TSO fulfills a similar purpose to Unix login sessions...

 (TSO). It initially supported

• Binary Synchronous Communications
  Binary Synchronous Communications
  Binary Synchronous Communication is an IBM link protocol, announced in 1967 after the introduction of System/360. It replaced the synchronous-transmit-receive protocol used with second generation computers. The intent was that common link management rules could be used with three different...
  
   (BSC) terminals
• start/stop terminals
• 2260 terminals
  IBM 2260
  The text-only 960-character monochrome IBM 2260 cathode ray tube video display terminal plus computer keyboard was a 1964 predecessor to the more-powerful color text-and-graphics IBM 3270. The 2260 screen image was normally configured with 12 lines of 80 characters each, which corresponded to IBM...
  
  
• message queuing in storage and on disk

Support for 3270 terminals

IBM 3270

The IBM 3270 is a class of block oriented terminals made by IBM since 1972 normally used to communicate with IBM mainframes. As such, it was the successor to the IBM 2260 display terminal. Due to the text colour on the original models, these terminals are informally known as green screen terminals...

was soon added.