Application Notes:
Please refer to the schematic for a better understanding of this section.
Refer to the ICA-202D Intercom Amplifier installation manual, (For application examples see pages
24 & 25). Refer to the PA-402 Power Amplifier installation manual.
The ICR-116 is suitable for any Intercom System requiring Multiple Station Selection. However, these
examples refer to use with other Tech Works products.
Each Station consists of a Speaker, which is also used as a Microphone (Half-Duplex Operation)
and a Call-In Switch.
Stations are selected by energizing that Stations Relay
Some control systems have Sinking Relay Drivers (Pull to Ground), while other control systems have
Sourcing Relay Drivers (Pull to +24Volts). The ICR-116 accommodates either type driver (See
Jumper Options).
When the Relay is energized, the Intercom Amplifier is connected to that Station
’s Speaker.
When a Relay is not energized, the Station Speaker is terminated by two 200-Ohm resistors tied to
COMMON. The Termination serves two purposes; reducing crosstalk, bleeding off static electricity.
When listening normally, only one relay is energized at a time. However, during (Zone) Paging, many
or all relays may be energized simultaneously.
When stations are selected,
good design practice
sequences the Intercom Amplifier to avoid
listening Pops. The ICA-202 has a Mute input, which simplifies this implementation. The selection
sequence is Mute Intercom, Select Station, wait ~100mS, Un-Mute Intercom. The de-selection
sequence is Mute Intercom, De-Select Station. The new selection sequence is Mute Intercom, Select
new Station, wait ~100mS, Un-Mute Intercom.
Station Call-in Switches have a Common Return
The Call-In Switches are separate circuits from the audio pathways.
Some control systems Reference
the Call-In Switched to the Relay Power Supply Negative Rail. Some control systems Reference the
Call-In Switched to the Relay Power Supply Positive Rail. Some control systems Reference the Call-
In Switched to a Logic (PLC) reference. The ICR-116B accommodates any type of reference (See
Jumper Options).
The Paging Relay
(s)
may be used in systems where the Intercom Amplifier has insufficient
Power
When the Paging Relay(s) are energized, selected Stations are connected to the Paging Amplifier
output. This is especially easy to implement using Tech Works Intercom Products. The ICA-202D
“Paging Audio Output” connects to the PA-402 Paging Amplifier “Paging Audio Input”. The ICA-202D
and PA-402 Page Logic control inputs are tied together. The PLC Energizes the Page & Station
Relays, and then pulls the Page Logic inputs to Common.
