Overview

The Philips Avalon Toco+ MP Transducer (M2735A) is the most capable wired Smart Transducer in the Avalon family. It combines four measurement modes — external Toco for uterine activity, Smart Pulse for maternal pulse, fetal scalp ECG (DECG), maternal ECG (MECG), and intrauterine pressure (IUP) — into a single transducer body. The “+” in the name refers to the auxiliary 7-pin D-type connector on the transducer housing, which accepts a DECG, MECG, or IUP adapter cable. The “MP” suffix refers to the integrated Smart Pulse feature, which uses two built-in infrared sensors to measure maternal pulse continuously whenever the transducer is in contact with the patient’s abdomen. Smart Pulse is patent-protected by Philips and runs automatically without any additional SpO2 sensor, ECG electrodes, or operator input. The M2735A is plug-and-play with any Avalon FM20, FM30, FM40, or FM50 fetal monitor via the standard D-shaped Smart Transducer connector, and it shares the same digital signal processing architecture as the rest of the Avalon Smart Transducer family. Each transducer contains its own CPU and signal-processing board, so adding the M2735A to a monitor does not place an additional processing burden on the host — the transducer delivers its measurement result as a digital data stream.

Toco Measurement and Smart Pulse

External Toco measurement is performed by a pressure-sensitive strain gauge resistor bridge inside the transducer housing. The strain gauge requires a DC excitation voltage, and its differential output is proportional to the pressure applied to the transducer surface as the maternal abdomen hardens during a contraction. The signal is digitized by an A/D converter inside the transducer and sent to the monitor as processed data. Smart Pulse, the “MP” function, runs in parallel: two built-in optical sensors emit low-power infrared light comparable to a TV remote and detect the reflected signal from the maternal abdomen, allowing the transducer to derive maternal pulse without electrodes, cables, or a SpO2 sensor. When the M2735A is applied, Smart Pulse becomes available a few seconds after contact is established. Maternal pulse is then continuously compared against any fetal heart rate channels on the monitor via Cross-Channel Verification (CCV), which alerts the clinician when a fetal channel and the maternal channel begin tracking the same rhythm — the classic signal-ambiguity scenario where the maternal pulse is mistaken for fetal heart rate.

DECG, MECG, and IUP via Adapter Cables

The auxiliary 7-pin D-type socket on the M2735A accepts one of three Philips adapter cables, each of which automatically configures the transducer for the corresponding measurement mode. The M1362B DECG Reusable Legplate Adapter Cable connects to a Philips fetal scalp electrode (such as the 15133E Qwik Connect Plus Spiral Electrode) via an M1349A attachment electrode, and the transducer captures the fetal cardiac signal directly from the presenting part. The M1363A MECG Adapter Cable connects to two pre-gelled foam electrodes applied to the mother for maternal ECG capture, useful for high-acuity cases where direct rhythm monitoring is needed alongside obstetric trending. The M1334A Adapter Cable TTIUP connects to a Koala-style disposable sensor-tip intrauterine pressure catheter for direct uterine pressure measurement, used in labor management cases where external Toco does not provide adequate pressure resolution. Mode detection is automatic — an external mode resistor inside each adapter cable identifies itself to the transducer’s frontend so the user does not need to navigate menus to switch between modes. The ECG frontend is a 3-lead system (RA, LA, and reference) with ESD-protected inputs and a 16-bit A/D converter shared with the IUP channel.

Software Versions and Platform Evolution

The M2735A Toco+ MP Transducer requires the appropriate Avalon FM-series monitor software to expose its full measurement set. Avalon fetal monitor software has evolved through several major releases — early Avalon platforms shipped with software revisions in the F, G, and H families, which supported the original Toco transducer (M2734A) and the Toco+ transducer (M2735A) for DECG, MECG, and IUP but did not yet expose Smart Pulse functionality. Smart Pulse was introduced with the J-series software releases. Specifically, the integration of Smart Pulse into the Toco MP and Toco+ MP transducers requires Avalon fetal monitor software revision J.3x.xx or later, sometimes referred to as “Rel. J.3” in Philips application notes. From J.3 onward, the monitor exposes Smart Pulse maternal pulse as a separate numeric and trace channel and uses it as a CCV input alongside any active fetal channels. The DECG/MECG/IUP capabilities of the M2735A continued to work on earlier software but without the maternal pulse cross-check that Smart Pulse provides. Hospitals running pre-J.3 Avalon software may need a service upgrade before deploying the M2735A in its full Toco+ MP configuration. IPR Medical can confirm the software revision installed on a monitor at the time of refurbishment and advise on upgrade paths through Philips authorized service.

Clinical Workflow and Belt Attachment

The Toco+ MP attaches to the patient with a standard Avalon abdominal belt; the integrated belt button on the transducer housing accepts buttonhole belts directly, and for belts without buttonholes a butterfly belt clip is supplied with the system. The transducer should be applied without gel or water between the skin and the transducer surface, because conductive media can compromise the Toco baseline and interfere with Smart Pulse infrared reception. When the transducer is applied, Smart Pulse activation is automatic — no operator action is required. Each transducer features a Finder LED on its housing; when the clinician touches the corresponding FHR or maternal numeric on the monitor’s touchscreen, the LED on the matching transducer illuminates, eliminating ambiguity over which transducer is producing which trace. This is particularly useful in twin and triplet monitoring scenarios where multiple US and Toco transducers are in use simultaneously. The M2735A is rated for use on the maternal abdomen in routine antepartum surveillance and intrapartum labor monitoring, and the auxiliary connector remains accessible while the transducer is belted in place, so DECG, MECG, or IUP can be initiated mid-labor without removing the Toco transducer.

Trending, Cross-Channel Verification, and Clinical Decision Support

All measurements from the M2735A — Toco, Smart Pulse, DECG, MECG, and IUP — are presented on the Avalon monitor display as numerics and waveform traces and are recorded to the integrated fetal recorder paper trace. The host monitor’s Cross-Channel Verification (CCV) function continuously compares every fetal channel against every maternal channel and posts an on-screen indicator when two channels begin tracking the same rate, helping the clinician identify maternal-for-fetal confusion before it affects clinical decision-making. When Smart Pulse is the source of the maternal pulse rate, the monitor does not produce an audible QRS tone and certain alarm behaviors are suppressed per Philips’ Instructions for Use, because Smart Pulse is intended as a coincidence-detection input rather than a primary alarm source. The recorder offset, paper scale, and recorder speed settings are managed by the host monitor, not by the transducer itself. Data captured during a monitoring session can be exported to Philips OB TraceVue or IntelliSpace Perinatal (ISP) over the monitor’s LAN connection, where it becomes part of the patient’s electronic obstetric record.

Network and EMR Integration

The Toco+ MP itself does not have a network interface — all connectivity is handled by the host Avalon FM-series monitor. On the FM20 and FM30, integration with OB TraceVue or IntelliSpace Perinatal is available over RS232 or LAN; the FM40 and FM50 add additional LAN capabilities and, on FM50, a VGA output for an external display. Once the transducer is connected to a network-enabled Avalon monitor, all M2735A measurement data flows through the monitor’s clinical data interface to the perinatal information system. There is no separate firmware on the transducer that requires hospital network access — the transducer’s onboard CPU stores calibration, country-specific configuration, and error logs in a serial EEPROM, and the monitor reads this data over the D-shaped Smart Transducer connector at plug-in. From a clinical engineering perspective, this means software and configuration changes affecting M2735A behavior live on the host monitor, not on the transducer, so transducer swaps are truly plug-and-play and do not require post-installation configuration.

IPR Medical — Buy, Sell, Repair, and Parts

IPR Medical buys, sells, and repairs the Philips Avalon Toco+ MP Transducer (M2735A) and stocks the OEM and OEM-equivalent parts needed to keep it in service. Common repair scenarios on the M2735A include cable damage at the strain-relief boot, intermittent contact at the D-shaped main connector, and damage to the 7-pin auxiliary D-type socket caused by side loading from adapter cables. IPR Medical can quote a full functional refurbishment that includes connector inspection, cable replacement where required, full Toco/Smart Pulse/DECG/MECG/IUP functional testing per Philips service manual procedures, and electrical safety testing. IPR Medical also stocks compatible Avalon abdominal belts, butterfly belt clips, M1362B DECG legplate adapter cables, M1363A MECG adapter cables, M1334A IUP adapter cables, and disposable spiral fetal scalp electrodes and attachment electrodes. Facilities with surplus Avalon transducers from monitor fleet retirements can contact IPR Medical for an evaluation and offer.

IPR Medical buys, sells, repairs, and stocks parts for the Philips Avalon Toco+ MP Transducer (M2735A). Contact IPR Medical at 855-477-8866 or cs@iprmed.com with service or software questions.

Trademark Notice: Philips, and all other brand names, model names, and part numbers shown are trademarks of their respective owners and are used on this page only to identify the original manufacturer’s equipment offered here, consistent with nominative fair use. This listing is offered by IPR Medical, an ISO 9001:2015-certified independent service organization, and is not sponsored by, affiliated with, or endorsed by Philips.