The PAD-5 provides two bell follower applications for its NACs. The first, the bell follower, behaves in the same manner as the PAD-3 or PAD-4. When selected, a PAD-5 NAC will mimic a signal that appears on the Bell Follower Input (BFI). No additional control logic is required.
The Gated Bell Follower (GBF) adds the feature where the connection between the BFI and the NAC configured as a GBF NAC (GBFN) only begins once the PAD-5’s GBFN is commanded to activate. This allows selective GBFN activation via system control logic when separate zoning is required. These activation commands are sent via the P2 line card to the PAD-5. It can also be used to provide synchronization of audible/visible signals across multiple P2 line cards (see Figure 12 below). Refer to Figure 11 for a representation of the logic in the PAD-5 for the GBF feature.
The GBFN application includes a degrade mode which monitors the BFI. When a GBFN is activated, if no signal is seen on the BFI for six seconds or longer, the GBFN will revert to the highest active priority NAC pattern selected in the configuration tool for the GBFNs. Once a BFI input signal is seen, and for as long as the GBFN remains active, the BFI is monitored. A loss of BFI input exceeding 65 seconds during the active GBFN period will also activate the degrade mode.
All the PAD-5s on a given P2 line card are synchronized. Synchronization between multiple P2 line cards is not provided. Refer to the following section for a GBF application to address this situation.
All the features of the GBFNs on the main PAD-5 are also available on the Class A expansion card.