Novation's first CAT was an external 300 bit/s Bell 103-standard modem that connected to the phone lines using an acoustic coupler. Like most other acoustically coupled modems, the CAT required the user to dial the desired number on a normal telephone, and then press the handset into rubber cups on the modem if a carrier could be heard. This was only possible because telephones were generally available only from Western Electric, all of a standardized size and layout. There was no sort of automated operation available; even hanging up had to be done manually by returning the handset to the telephone and thereby pressing the hook button.