Termination Board; Termination Board - Tb; Matrix Termination Board - Mtb - Philips SM40 Instructions For Use Manual

5. SM40 MODULES
5.2 Termination Boards
Termination Board LBB 1377 (TB)
Matrix Termination Board LBB 1371 (MTB)
Relay Termination Board LBB 1379 (RTB)
Interconnection board mounted on the 19 inch frame back side, connecting:
a) 8 input sources (call stations and music sources) to the SM40 Centre.
b) SM40 Centre to the audio inputs of a maximum of 16 amplifiers.
c) The SM40 CRC's to the control inputs of 8 SQ45 amplifiers (break contacts), and/or to 8 loudspeaker
volume control override circuits (make contacts).
Transformers may be mounted on TB (LBB 1377) to avoid earth(ground) loops when the system is
interfaced with domestic music sources.
d) The CRC's to switch the 100 V output of the SQ45 amplifiers (see section 5.2.3)
The task of the termination boards described here is to connect the central rack unit of the SM40 Public
Address Distribution Centre to external equipment.
A maximum of 5 boards can be mounted on the rear panel of each rack frame, which hinges down to expose
the boards for service.
The use of push fit support studs to mount the boards onto the back panel makes fitting or removal a fast
and simple matter.
Each termination board is connected to the Interconnection Board (IB) by flat cable and/or individual wires
fitted with female Pressfit connectors.
Call Stations and amplifiers are wired (as shown), to screw connector blocks which are plugged into sockets
mounted on the termination boards. This has the advantage that if, for some reason, an SM40 rack frame,
or a TB, has to be removed, the screw connector block is simply unplugged, leaving the peripheral
equipment wiring intact. This avoids the tedious and risky business of rewiring the blocks in their original
configurations.
5.2.1

Termination Board - TB

The Termination Board (TB) has a total of 2 x16 screwblock connectors, and is capable of carrying out
several different functions:
1. Connection of Call Stations (CST)s and auxiliary input sources such as a background music player,
cassette player, etc. to 8 audio inputs of the SM40 Centre.
2. Connection of up to 16 SM40 Centre audio outputs to the inputs of 16 SQ45 amplifiers.
3. Connection of the 'break' contacts of the Control Relay Cards (CRC)s to the volume control override
inputs of SQ45 amplifiers.
4. Connection of the CRC 'make' contacts to the volume control override circuits which override the
volume control settings of individual loudspeaker cabinets.
If encountering the disturbing effects of an earth (ground) loop, up to 8 'galvanic separation' transformers
(for which the board of the LBB 1371 is pre-drilled) may be mounted. These transformers isolate the earth
(ground) of the input source equipment from that of the SM40 system.
5.2.2

Matrix Termination Board - MTB

Matrix Termination Board LBB 1371 (MTB) is used to suppress any small clicks which may occur when
outputs from the matrix are wired directly to an amplifier. A standard TB may be used when the signal is
routed via a TCC or similar buffering device.
(2 per Basic System)
(1 per Basic System)
LBB 1377/00
5
LBB 1371/00
5-5