What is CT2 Cordless Standard
CT2 cordless standard is the second generation of cordless phones that were first employed in Britain in 1989. This generation of cordless phones was based on digital technology and had many an advantages over its analog predecessor. It was designed for use in both home and office environment. The following points provide a brief overview about the technology and the features of this generation of cordless phones:-
Because of the use of digital technology, the cordless phones had better speech quality, were more resistant to interference, noise and fading as compared to the earlier generation. The digital signals were also very hard to intercept and decode, and thus provided a high level of security. The user needed to enter a PIN number in the cordless phone to gain access to it. Thus it provided safety against misuse if the handset fell in to the hands of a stranger. The system was allocated a bandwidth ranging from 864.10 MHz to 868.10 MHz and the channel allocation to the users was on dynamic basis. Forty channels were assigned in this range, each having a bandwidth of 100 KHz. The digital modulation technique that was used in this generation of handsets was Gaussian Frequency shift keying. It also employed Time Division Duplexing between the forward and the reverse link. A CT2 frame consisted of 2 ms, the reverse link from handset to the cordless base set supported in the first 1ms while the forward link from the base set to the portable handset supported in the next 1ms of the frame. Thus because of the use of TDD, only one 100 KHz channel was employed for two way communication between the base set and the portable unit. Each channel supported a data rate of 72 kbps with 32 kbps each for the forward and the reverse link. The rest 8 kbps was used for control signals. Speech waveforms were coded using ADPCM at a rate of 32 kbps.
The CT2 Standard defined a three layer interface for communication between the Cordless Fixed Part (CFP) and the Cordless Portable Part (CPP). Layer 1 dealt with the TDD technique, data multiplexing, link initiation and hand shaking. Layer 2 dealt with data acknowledgement and error detection and link maintenance. Layer 3 dealt with the protocols used to connect the Cordless Set to the PSTN.