Theory of Operation, Loop Start Interfacing

Theory of Operation

Loop Start Interfacing:

The TAMB2 provides a 24V DC talk battery on its T (tip) and R (ring) terminals. When it detects a DC loop current flow through these terminals, it will activate. Upon activation, it will produce an announcement tone and connect in the paging amplifier through an isolation transformer. The announcement tone can be set to be heard only at the paging phone or at both the phone and over the paging system. The TAMB2 allows bi-directional audio, both to and from the paging equipment

Ground Start Interfacing:

In addition to the tip and ring connections to this port, an additional connection between the TAMB2ʼs G/S terminal and the PBX ground must be established. When idle, the TAMB2 opens an internal relay contact in series with its T (tip) terminal, and monitors for loop current flowing in its R (ring) terminal. When the PBX grounds the TAMB2ʼs R terminal, loop current flows and is detected. The TAMB2 responds by closing the relay contact in series with its T terminal. Once this connection is established, the TAMB2 will produce an announcement tone and connect in the paging amplifier through an isolation trans- former. The announcement tone can be set to be heard only at

Trunk Timer Feature:

When interfacing to either loop or ground start trunks, a Trunk Timer feature can be enabled which will interrupt loop current flow to the PBX port for 1 second after either the VOX or Default time has expired. In many PBX systems this break in loop current will cause the connection between the TAMB2 and the calling station to be cleared, allowing another caller to access the paging system. This is designed to protect the

Station Port Interfacing:

The TAMB2 answers the station port after it detects high voltage (90V) ring on the line. The unit can be set to answer the call immediately or after the end of the first ring burst. Once answered, the unit provides an announcement tone and con- nects the telephone line to the paging amplifier through an iso- lation transformer. The announcement tone can be set to be heard only at the paging phone or at both the phone and over the paging system. The TAMB2 allows bi-directional audio, both to and from the paging equipment (in the case of talk- back paging equipment). Since the TAMB2 cannot directly determine the state of the calling partyʼs phone, it must use

(in the case of talkback paging equipment). Disconnection of the page happens when the loop start trunk goes on hook and loop current flow stops. In this mode, the TAMB2 responds to the status of the loop current flow and generally no timers are needed to control when it disconnects. However, a Trunk Timer feature is provided that can help prevent accidental lock-up of the paging system (see featureʼs description below).

the paging phone or at both the phone and over the paging system. The TAMB2 allows bi-directional audio, both to and from the paging equipment (in the case of talkback paging equipment). Disconnection of the page happens when the ground start trunk goes on hook and loop current stops. In this mode, the TAMB2 responds to the status of the loop current flow and generally no timers are needed to control when it dis- connects. However, a Trunk Timer feature is provided that can help prevent accidental lock-up of the paging system (see featureʼs description below).

paging system from a phone that may have been hung up incorrectly and is locking out access to the paging system. In addition to enabling this feature, the Default time period must be set and/or the VOX timer must be enabled and its time set. Both timers do not have to be used, but at least one must be enabled for this feature to work.

indirect methods to determine when to disconnect. Discon- nection of the TAMB2 from the call is controlled through 3 methods. 1) A default timer will drop the call after a preset amount of time has elapsed (1-200 seconds), 2) A VOX timer will drop the call after it detects no audio for a preset amount of time (1-11 seconds), 3) The unit will immediately drop the line if it detects a CPC pulse (break in loop current) from the PBX/CO port. Any of these disconnection methods can be in- hibited, however at least one must be enabled to ensure that the TAMB2 will disconnect.