The Whozz Calling? detects when the phone is on-hook and off-hook. This allows the unit to determine the length of each phone call and report this detailed information to the software. Telephone monitoring equipment can detect the occurrence of the On Hook and Off Hook status of the phone line by two methods. It can either sense the voltage on the phone line itself or sense current flow on a phone line passed through the equipment.
Voltages on incoming central office (CO) phone lines are consistent among all branches throughout a physical location (building). If the voltage levels are in standard range, monitoring equipment functioning in a voltage detection mode is able to sense On and Off Hook on any branch in the building. The obvious advantage to this detection scheme is that the monitoring equipment can be connected in parallel to the CO lines. Your unit comes from the factory set to voltage detection mode because, in most locations, this detection scheme works properly.
Current on phone lines only flows to the telephone device that is Off Hook. Monitoring equipment that senses On and Off Hook by means of current flow must be connected between the phone company’s incoming line and the device(s) that goes Off Hook. The current will flow through the monitoring equipment to the Off Hook device. With this detection scheme, any telephone device that makes or receives phone calls must be attached in series (i.e. to the output jacks) “behind” the monitoring equipment.
In order to sense the voltage on the phone line, the unit’s circuitry must draw a small amount of current from the phone line. The current draw is very small (70 mA, similar to a voltmeter), and is drawn when the phone line is On Hook. The telephone company’s amplifier supplying the power to your location may not be able to supply this current and still keep the On Hook voltage level within the standard range. This occurs primarily in older residential and commercial locations. An unsophisticated telephone company repair technician may diagnose this small current draw by the unit as a “short” on the line. Therefore, the telephone company will not address the shortcoming of their supply amplifier. If this situation occurs, the unit cannot be used in the voltage detection mode, it must be reconfigured to the current detection mode.
In order to configure the unit to a different Caller ID signaling format, the top of the enclosure must be removed and shorting jumpers moved on the circuit board. Use the following steps and refer to Fig. B1on the next page.
Remove power to the unit.
Remove the top of the enclosure by first removing the four Phillips head screws on the bottom of the unit.
Slide the top of the enclosure off.
Locate the shorting jumpers on the circuit board (2 per channel and 1 main jumper) used for configuring the unit to Current Detection (refer to Fig. 8 on the next page).
Slide off the appropriate jumper(s) and reconnect as per Fig. 8.
Replace the top of the enclosure and replace the four screws.
