The Fylde PCM Switch is a fully BABT approved audio switch for use in the MPT1327 trunked infra-structure and patches lines to enable the multi-site audio paths to be realized.

Where the RCP is, effectively, a data switch, the PCM Switch is an audio switch. However, the PCM is in essence a dumb switch and will not operate in a trunking environment without the control (via an RS232 cable) from the RCP.

Audio Routing
There are two main types of audio connection into the ports.

The first is a leased line (or microwave link) between the port and the inter-site channel on a trunked site. It follows, then that if you need an audio link between the inter-site channels on each site and the switch port allocated for that channel that you would want to limit the number of channels with this expensive audio link. This can be done through very careful planning of the system long before any installation is carried out.

Where facilities exist, ISDN can be used for the speech circuits on a dial-up basis. However, when using this, a suitable ISDN modem with DTR dialing is required.

The second type of audio connection is the connection to a telephone gateway, either a private PABX or the PSTN of the country where the equipment is installed.

When both of these connections are achieved, multi-site calls and telephone interconnect calls can be made from any site in the system (as long as that site has an inter-site channel available).

The Four-Port Card
Each card provides four audio ports via JT45 sockets. The only limitation here is that on any single card, there are only 2 ports available for PABX or PSTN connection. However, when allocating ports to multiple cards, this does not appear to be a restriction. For example, with any multi-site system, more than 50% of the ports will be used for inter-site channel connections.

Connections to the PCM Switch
PSTN
PABX
2-wire
4-wire
E&M
Loop Disconnect (US Standard)
Ground Start (US Standard)