Based on the protocol,assume the channel width needs to be twice the range of frequencies used. How wide must the band be to accommodate 100 channels?
In figure, the 2 KHz tone is indicated by (1), and the point in time at which the mobile goes off hook, a 2.15 KHz tone is transmitted (2) on the channel as a signal that the mobile wishes to use this preselected free channel. The figure includes the term OOFF hook which is derived from the classical wired telephones where access to the wired line is accomplished by lifting the receiver from the hook switch, i.e., the phone is said to be placed in the off hook state.
In order to provide a means of indicating that the 2.15 KHz tone is not just a spurious tone or some noise in the atmosphere, the mobile removes that frequency and transmits a 1.699 KHz tone (3). This logical change of state represents a form of intelligence in the request for the use of the particular channel where it is highly unlikely that these two frequencies would appear in the medium due to noise causing the indicated transition is very small, and the system can assume that the mobile device has in fact requested that particular channel, and the system responds with sending the 1.830 MHz tine as feedback which indicates to the mobile that is now has control of the channel. At this point, other mobiles do not see the 2 KHz tone and are looking for the next free channel (2 KHz) to monitor or to use for a mobile initiated call.