This Tecpro based wired Theatre & Church Intercom belt pack communication system with Altair headsets will get you up and running in most Theatres, Schools and Colleges. 
It is simple to use and all you will require …

Genuine Canford Audio Single channel beltpack BP511
ABS Case.  Loop through XLR 3 pin for use with standard mic cable
XLR4 headset connection
Canford Part Number 27-511
Recessed controls  Swivel belt cli…

Genuine Canford PS751 Tecpro Intercom Power Supply.
The PS751 will power up to 45 x BP511 or  50 x BP111 beltpacks.
Canford Audio Part Number: 27-751 The PS751 features 1 Channel Maximum current 2 Amp, O…

Canford Tecpro MS741 Theatre intercom master station.
Dual channel with loudspeaker.
Replaces the MS 721 and MS 731
Canford Tecpro Part Number: 27-741