MC66
This page helps you identify the MC Technologies MC66-W RS232 modem and check the modem label, LED status, antenna connection, power connection, and SIM card. The MC66-W is a 2G GSM/GPRS modem, so it needs an active SIM card, 2G network coverage, and a correctly connected external antenna to communicate.
The MC66-W only supports 2G GSM/GPRS. If your mobile operator has shut down 2G in your area, the modem cannot connect regardless of SIM, antenna, or LED status. Check with your SIM provider that 2G is still active on the network and on your subscription before troubleshooting hardware.
Identify the modem
Check the label on the modem.
| Specification | Value |
| Modem type | MC-Technologies MC66 |
| Housing color | Blue |
| Network | 2G GSM/GPRS (Quad-band 850 / 900 / 1800 / 1900 MHz) |
| Power | 8–30 V DC |
| Antenna connector | SMA male |
| SIM | Mini-SIM (2FF), 1.8 V or 3 V |
LEDs
The modem has two LEDs:
- The red LED shows power control and controller status.
- The yellow LED shows the modem’s GSM/GPRS network and communication status.
Use the blink pattern, not only the colour, when identifying the modem status.
Red LED
The red LED indicates the power control and the status of the modem controller.
| LED status | Value |
| Off | Power connected, modem not switched on (Sleep mode) |
| Flashing | Modem switching on — serial interface will be active within a few seconds |
| Off (during active mode) | Modem active — yellow LED will be flashing |
| Solid on | Standby mode (~30 seconds); modem will activate immediately on ignition or DTR signal |
Yellow LED
The yellow LED shows the modem’s network and communication status. On some units the yellow LED may look red through the casing, so use the blink pattern to identify the status.
| LED mode | Value |
| Permanently off | Modem is in one of the following modes: POWER DOWN mode NON-CYCLIC SLEEP mode CYCLIC SLEEP mode with no temporary wake-up event in progress 1) |
| 600 ms on / 600 ms off | Limited network service: no SIM, no PIN, network search in progress, or login in progress. |
| 75 ms on / 3 s off | IDLE — registered, no data session. |
| 75 ms on / 75 ms off / 75 ms on / 3 s off | GPRS context active — ready for data. |
| 500 ms on / 50 ms off | Packet data transfer active. The modem is currently sending or receiving data. |
| Permanently on | Voice or data call connected to remote party |
Antenna
The MC66 uses an external antenna connected to the modem’s SMA male antenna connector. The antenna cable must therefore have an SMA female connector. Use a quad-band GSM antenna that supports:
| Antenna requirement | Value |
| Connector on modem | SMA male |
| Connector on antenna cable | SMA female |
| Supported frequency bands | Quad-band GSM 850 / 900 / 1800 / 1900 MHz |
SIM card
The MC66 uses a SIM card to access the mobile network.
The SIM card must be active and allowed to use 2G GSM/GPRS on the mobile operator’s network. The SIM PIN should be disabled unless the connected system is configured to enter the PIN automatically.
Modern SIMs are often supplied as nano-SIM or micro-SIM inside a punch-out frame. Make sure the SIM is the correct size for the modem’s SIM card reader before inserting it. Do not insert a loose nano-SIM or micro-SIM directly into a larger slot.
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