Clear-Com MT1 Intercom System Isolation Box

The MT-1 party-line isolator circuit card is an accessory for Clear-Com partyline systems that will electrically isolate the ground, power, and signaling of two intercom systems. If two power supplies or main stations are connected together in a system but located in different buildings or on different AC power systems, an objectionable “hum” may be caused by a ground loop. The MT-1 will eliminate the “hum” by breaking the ground loop between the powered stations. This device also allows channels from two separate Clear-Com systems to be connected together and because of the power isolation it provides, each system can be shut down independently. In addition, the system isolator will pass the “Call” signaling from one system to the other with complete electrical isolation. The MT-1 offers transformer isolation for the audio signal and opto-isolation for the “call” signal. It also provides the termination for both systems.

Features:

• Electrically isolates ground, power, and signaling of two intercom systems
• Breaks the ground loop between power stations to eliminate “hum”
• Allows independent shut down of two connected intercom systems
• Transformer isolates the audio signals
• Opto-isolates the “Call” signals
• Provides termination for the connected intercom systems

Specifications:

• General:
  • Line Level: -14 dB nominal, +10dB max
  • Call Signaling Voltage: 11 volts DC on audio line
  • Call Signal Sensitivity: 4 volts DC
  • Call Signal Delay: 50 mS
  • Power Source: Passive, via intercom line
• Connectors:
  • Line: 3-screw terminal block for each intercom line
• Isolation:
  • Voltage: 120 VAC max
  • CMRR: 65 dB min
• Audio:
  • Insertion Loss (each direction): 3 dB nominal
  • Frequency Response: 100 Hz - 20 kHz +/- 1 dB
  • Distortion: 0.1% THD at -10 dB input, 100 Hz - 20kHz
• Dimensions: 1.25" H x 2.88" W x 1.88" D (30 mm H x 73mm W x 47mm D)
• Weight: 2.25 oz (0.07 kg)