Feature Overview: Smart Relay

Algo’s Smart Relay Design: No Ordinary Relay

Detecting “Normally Open” and “Normally Closed” Contacts

Relay inputs are capable of more than simple detection of “normally open” or “normally closed” contacts (which are configurable through the web interface). The term “Smart” is used to describe these inputs for their ability to provide power and measure current flow.

In the case of monitoring an external contact, it is typically preferred to use a “normally closed” contact since wire breaks or disconnects are more probable than wiring shorts. A broken or detached wire in “normally closed” contacts will look like an open and cause the event intended to be triggered. If a “normally open” contact is used and a wire break occurs, it would go unnoticed.

Examples of Smart Relays in Algo IP Endpoints

In the 8028 IP Doorphone, the relay input may be connected to a door contact to detect when the door is open. This has many purposes, such as deactivating a door strike to prevent tailgating, detecting a door jammed open with a rock, or ceasing a telephone ring when the door has been opened.

Another example is in the 8301 IP Paging Adapter, where the relay input may be used with an emergency button to initiate a multicast alarm, to call customer service, or play a pre-recorded announcement. In a speaker device, such as the 8188 Ceiling Speaker, the relay input may detect a door opening and play a chime in response.

Four State Detection

The smart relay input may be used with end-of-line (EOL) resistors for four-state detection: fault open, fault shorted, idle normal, and trigger. This helps with anti-tamper capability and system supervision beyond the IP endpoint itself.

Supervision of Relay Inputs in Algo Products

The 1202 and 1203 call buttons are backlit which allows a user to see that they are in working order. The backlighting is illuminated by power provided from the smart relay input which is used as a method of supervision. The normal state for these buttons is a precise amount of current. Button activation changes the current, which triggers the specific event the connected IP endpoints have been configured for. The IP endpoint can detect a wire short or disconnect for fault detection and supervisory capability.

Smart Relay for Volume Control

For Algo’s IP Speakers, the smart relay allows connection of the Algo 1204 for a ten-choice setting volume control. Analog paging technology typically uses an attenuator in series with one or more speakers to control the output level. Using the 1204, the dial is not in series with the speaker, however, it provides information to the speaker regarding the desired volume output level. This enables features such as adjustment of standard paging volume while allowing the speaker to play at full volume for an emergency notification, class change bell, or other such event. In effect, the “smart” relay input turns the 1204 into a “smart” volume control.

Smart Relay for Multicasting

Using Algo’s 1205 Audio Interface connected to the Algo 8301 IP Paging Adapter, the relay input from the 8301 can detect the three states of the 1205 switch for multicast streaming. The knob of the 1205 can be turned to either have the multicast stream off, use the attached handheld microphone, or stream music from a connected smartphone. No ordinary relay input can perform this function.