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I recently had a chance to play with one of the last bastions of high-quality analog modem technology, a MultiTech MultiModem II, 5600 series. It’s an extremely high quality device which can do things such as automatically dialing a stored number when DTR goes high. These are quite useful as diagnostic backup devices and are often found connected to enterprise-class equipment to allow tech support another channel in or to allow the device to send emergency error messages.
Since I had access to this I decided to open it up and look inside, since tech like this isn’t too common these days. Photos of the MultiTech MultiModem II (5600 Series) disassembly (such as the one above) can be seen here in this gallery.
In the two photos showing the two sides of the PCB (top · bottom) here’s the components I found most interesting:
· Conexant SM56D / CX06833-44: This is the heart of the device; the modem itself.
· Atmel ATF1502ASV: EEPROM CPLD (Electronically Erasable Programmable Read-Only Memory Complex Programmable Logic Device); likely where the front panel controls run and how the modem chip is controlled.
· LM7805 (x3): Three linear voltage regulators which seems to me like an old but very reliable method for getting smooth power.
· Intersil ICL3207ECBZ (x2): RS232 transmitters / receivers.
· Atmel 26C16AN: 16K serial EEPROM.
· Atmel AT49BV040A: 4-megabit (512K x 8) Flash Memory. (Hidden in photo by front panel bracket.)
· Fairchild Semiconductor 74LVX4245: Dual Supply Translating Transceiver. Converts between 3.3v and 5v busses; used to drive 5v logic in LCD display module. (Hidden in photo by front panel bracket.)
· LM386: Audio amplifier for modem speaker.
· Cypress Semiconductor CYIFS781BSXC: Spread spectrum clock generator designed to reduce EMI.
· 28.224 MHz Crystal: Connected to clock generator.