As you can see from the circuit diagram, the microphones’ capsule is short-circuited by one half of the push-
to-talk switch. This means that the output wires (White & Red) are a short-circuit when the PTT switch is not
pressed, thus preventing any signal at all reaching the amplifier.
When the PTT switch is pressed, this short-circuit is removed, and the audio from the microphone capsule is
fed into the amplifiers’ input. At the same time, the second half of the PTT switch places a short-circuit
across the Blue & Black wires and these may be used to trigger an external action e.g. the “Chime” in a local
device, such as the AVU2002 pre-amplifier/line driver.
IMPORTANT SAFETY NOTICE :-
For safety reasons, the shield (or screen) of the microphone cable must be earthed at the equipment end.
Most equipment with microphone inputs has its’ chassis at earth potential, but some (typically low-voltage
supplied devices) may not. It is the installers’ responsibility to ensure that the microphone is
adequately earthed!
TECHNICAL SPECIFICATIONS
MODEL CSM660B
TYPE Moving Coil Microphone
Polar Pattern Unidirectional
Impedance 600 Ohms, Balanced
Sensitivity -58db @1 KHz (0db = 1V Pa)
Frequency Response 100Hz-10KHz
Connection Cable 2 core shielded + 2 core cable
Cable Length 2.5m (8 ft 2 ins)
Terminal Connector 5 Pin DIN Plug
Weight * 440 g (0.97 lb)
Dimensions 100 (W) X 215 (H) X 150 (D) mm (3.9 X 8.5 X 5.9 Ins)
Talk Switch Push-to-Talk (Short off circuit, with locking lever)
Remote Switch Leaf Spring Contact (Interlocked with Talk Switch)
Finish HEAD : Zinc Plated Steel Wire, Baked Paint (Grey)
BODY : ABS Resin (Grey)
* Weight given in the above table does not include the connection cable or plug.
DOCUMENT NUMBER AVS/CSM660/OEM/01 REV 2.0 25
th
November 2005 Page 3 of 3