MHY 923
MHY 923
Input/output device
Element MHY 923 is addressable element of FDFAS

Element MHY 923 is addressable element of FDFAS, which is intended:

  • to control and sensing of following devices related to fire protection
  • to connection and reset of special sensors of FDFAS

in addressable FDFAS LITES with C.I.E. MHU 109 and Firexa, manufactured by LITES Liberec s. r. o. Element is connected to detection line of the C.I.E. The address is set by help of addressable preparation MHY 535.

It contains one separately controllable bi-stable relay and one input for transmission of information to the C.I.E. This input allows checking of connected outer device controlled by built-in
relay, or it is possible to set output as independent. On this output it is possible to connect e.g. aspiration detector, where it is simultaneously connected normally closed contact (fault) and
normally opened contact (alarm).

Relay output is activated according to kind of connection and setting in configuration program of C.I.E.:

a) from C.I.E after fulfilment of entered conditions independently or depending on state of input

b) automatically during reset of C.I.E.. Relay has a function for reset of connected detector.

Electrical circuits of element are on the printed circuit board, which is placed in a plastic box with removable lid. Element contains input circuit, which can be plugged either as opto-isolated or for connection of normally open or normally closed contact. Input can be connected as a balanced, monitored for interruption and short-circuit with the possibility of transmission of fault of connected device. In guarded regime the activation of input of element MHY 923, connected in system Firexa, is indicated by flashing of LED on element.

Addressable part registers a communication from C.I.E, logs on set address and transmits the information .about situation on input, QUIET, ALARM, FAULT).

The possibility of using the input/output element MHY 923



MHY 923 použití


Technical parameters
Power supply (18 až 21) Vimp
Nominal power supply (17 až 20) Vimp
Quiescent current (for credit to current of line) max. 200 µA
Input opto-isolated – voltage
Input voltage 9 V ÷ 30 V (logical 1), 0 V ÷ 3 V (logical 0)
Input resistance cca 10 kΩ
Input contact NO/NC
resistance of line and closed contact max. 1 kΩ
resistance of open contact min. 10 kΩ
output test voltage cca 19 Vimp
output test current max. 1,9 mA
Input guarded
test voltage 17÷20 Vimp
resistance of line max. 100 Ω
test current quiescent cca 0,95 mAimp
test current alarm cca 1,4 mAimp
test current detector fault cca 0,65 mAimp
resistance quiescent 10 kΩ
resistance alarm 4,7 kΩ
resistance detector fault 20 kΩ
Optical signalling (in regime v guarded input) red LED
Relay change-over contact max. 40 V, max. 1 A
max. 30 W, max. 40 VA
Setting of address (by preparation MHY 535) 1 – 128
Cross-section of attachable conductors (0,2 ÷ 1,5) mm²
Protection according to ČSN EN 60529 IP 40
Radio screening degree according to ČSN EN 55022 B-class equipment
Dimensions (w x h x d) (81 × 81 × 24) mm
Weight cca 95 g


Element MHY 923 is designed for connection to the safe device according to ČSN EN 60950 and fulfils requirements of standard for input/output devices ČSN EN 54-18.

During design of device it is necessary to ensure recommendations and measures to reduce the effects of interference voltages and rules for design of C.I.E.


Working conditions
Element MHY 923 is intended for stationary use in areas protected against weatherproof with classification according to ČSN EN 60 721-3-3:
K: climatic conditions for environment 3K5
working temperature range (-25 to +70) °C
relative humidity of air range max. 95 % při +40 °C
atmospheric pressure range (86 až 106) kPa
without condensation, ice accretion and ice formation
Z: special conditions 3Z1 thermal radiation negligible
B: biological conditions 3B1 without presence of flora and fauna
C: chemical active substances 3C1
S: mechanical active substances 3S1
M: mechanical conditions 3M1
Eminent temperature time duration (45 to 70) °C 2 months per year
Eminent humidity time duration (85% to 95%/≤ 40°C) 100 hours per year