Method for monitoring system access to a radio-communication system using an adjunct receiver where it begins to look for an assigned control channel for emergency calls made by mobile units

摘要

To provide terminal unit location for emergency call handling to emergency service centers 730, quasi-independent systems referred to as adjunct systems 712, 714, 716, are provided to monitor remote unit transmissions and derive location information for mobile units making emergency access calls. The adjunct receiver 712 listens to the channel frequencies associated with the system and the channel frequencies on which transmissions are received by the adjunct receiver are evaluated to determine whether the channel is a control or traffic channel. The identification of the control channels which the adjunct receiver is able to monitor is sent to the central processing center 720 which in turn identifies to the adjunct receiver the control channels the receiver is to monitor.